Develop Reference

Why "FindWindowEx" can't find RichTextBox component

I'm doing an auto program (C#,not C++), and I need to get a RichTextBox in a form. I have used the Spy++ to get the title and class name, but FindWindowEx always does not find RichTextBox, and GetLastError gets the word 0. And then this is a simple example.
IntPtr parent = FindWindow(null, "Form1");
if (parent!=IntPtr.Zero) {
//find test1 textbox
IntPtr child = FindWindowEx(parent, 0,null, "test1");
if (child!=IntPtr.Zero) {
SendMessage(child, 0x000c, 0, lParam: "test");
} else {
Console.WriteLine("textbox can't be found");
}
//find test2 richtextbox
IntPtr childRich = FindWindowEx(parent, 0, null, "test2");
if (childRich != IntPtr.Zero) {
SendMessage(child, 0x000c, 0, lParam: "test");
} else {
Console.WriteLine("richtextbox can't be found");
}
} else {
Console.WriteLine("Form1 can't be found");
}
But result is richtextbox can't find. Help me.

I don't really think this is the best approach but it's something.
For this specific case you can search for all the handlers in the Form and then change the one you want.
var iHandle = Win32.FindWindow(null, "Form1");
var allItems = Win32.GetAllChildrenWindowHandles((IntPtr)iHandle, int.MaxValue);
Win32.SendMessage(allItems[1], 0x000c, 0, lParam: "Now you can change the text!");
I've tested and the allItems[1] will always be the same item, I think It's the way the items are ordered in the winForm top to bottom.
I'm using a second class for the Win Methods:
public class Win32
{
public const int WM_SETTEXT = 0X000C;
public static List<IntPtr> GetAllChildrenWindowHandles(IntPtr hParent, int maxCount)
{
var result = new List<IntPtr>();
int ct = 0;
IntPtr prevChild = IntPtr.Zero;
IntPtr currChild = IntPtr.Zero;
while (true && ct < maxCount)
{
currChild = FindWindowEx(hParent, prevChild, null, null);
if (currChild == IntPtr.Zero) break;
result.Add(currChild);
prevChild = currChild;
++ct;
}
return result;
}
[DllImport("user32.dll")]
public static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);
[DllImport("User32.dll")]
public static extern int FindWindow(string strClassName, string strWindowName);
}
Edit: Method to get all children windows handles taken from: https://jamesmccaffrey.wordpress.com/2013/02/03/getting-all-child-window-handles-using-c-pinvoke-findwindowex/

GetWindowText hangs on Windows 10

TL;DR: Did GetWindowText win32 api change behavior on windows 10?
I have some code that loops through all windows on the desktop to find a window where the title contains some text.
When this code hits a window named "" with class "URL Moniker Notification Window" it hangs on GetWindowText.
GetWindowText is trying to send a message, my guess is WM_GETTEXT.
This window is part of the exe "SearchUI.exe", the process is suspended and can't process messages.
When reading: https://blogs.msdn.microsoft.com/oldnewthing/20030821-00/?p=42833/
according to rule 2, this should not happen.
This code has been working fine for years. (win 7, 8, 8.1)
So did GetWindowText change behavior in Windows 10?
Update:
The code in question.
public static int HwndGet(string partialTitle, string klassenavn)
{
partialTitle = partialTitle ?? "";
var cTitleTemp = new StringBuilder(255);
var hWndTemp = FindWindowEx((IntPtr)0, (IntPtr)0, null, null);
var nypartialTitle = partialTitle.ToUpper();
while (hWndTemp != (IntPtr)0)
{
GetWindowText(hWndTemp, cTitleTemp, cTitleTemp.Capacity);
string sTitleTemp = cTitleTemp.ToString();
sTitleTemp = sTitleTemp.ToUpper();
if (sTitleTemp.StartsWith(nypartialTitle, StringComparison.CurrentCultureIgnoreCase))
{
var className = new StringBuilder(255);
GetClassName(hWndTemp, className, 255);
//sTitleTemp: " + sTitleTemp + " ClassName: " + ClassName);
if (className.ToString().StartsWith(klassenavn, StringComparison.CurrentCultureIgnoreCase))
{
return (int)hWndTemp;
}
}
hWndTemp = GetWindow(hWndTemp, GwHwndnext);
}
return 0; // does not find the window
}
Stack trace:

The code you are using isn't "safe". There is no guarantee that the order of the windows won't change between calls to FindWindowsEx and GetWindow(GwHwndnext). For this reason there is another API, EnumWindows, that is "safe". You could try with it.
Here there is a sample program (based on the one found here).
public static class WndSearcher
{
public static IntPtr SearchForWindow(string wndclass, string title)
{
var sd = new SearchData { Wndclass = wndclass, Title = title };
EnumWindows(sd.EnumWindowsProc, IntPtr.Zero);
return sd.hWndFound;
}
private class SearchData
{
// You can put any dicks or Doms in here...
public string Wndclass;
public string Title;
public IntPtr hWndFound;
public bool EnumWindowsProc(IntPtr hWnd, IntPtr lParam)
{
// Check classname and title
var sb = new StringBuilder(1024);
int res = GetClassName(hWnd, sb, sb.Capacity);
if (res == 0)
{
throw new Win32Exception();
}
if (sb.ToString().StartsWith(Wndclass, StringComparison.CurrentCultureIgnoreCase))
{
sb.Clear();
res = GetWindowText(hWnd, sb, sb.Capacity);
if (res == 0)
{
int error = Marshal.GetLastWin32Error();
if (error != 0)
{
throw new Win32Exception(error);
}
}
if (sb.ToString().StartsWith(Title, StringComparison.CurrentCultureIgnoreCase))
{
hWndFound = hWnd;
// Found the wnd, halt enumeration
return false;
}
}
return true;
}
}
[return: MarshalAs(UnmanagedType.Bool)]
private delegate bool EnumWindowsProc(IntPtr hWnd, IntPtr lParam);
[DllImport("user32.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool EnumWindows(EnumWindowsProc lpEnumFunc, IntPtr lParam);
[DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
private static extern int GetClassName(IntPtr hWnd, StringBuilder lpClassName, int nMaxCount);
[DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
private static extern int GetWindowText(IntPtr hWnd, StringBuilder lpString, int nMaxCount);
}
and then use it like
IntPtr ptr = WndSearcher.SearchForWindow("classname", "windowname");

Retrieving name and/or text from a WinForms control using the WinAPI (CE)

I am trying to traverse the controls of a WinForms form (Windows CE) and retrieve/match their textual contents and names (that is, the Name property assigned to the WinForms Control object).
I do this from within a different process, thus WinAPI.
For traversing and for retrieving the text I wrote the following code. TextPresent uses DescendantControls for the traversing and Text to retrieve the text. I am fairly confident that the traversing code works correctly already - if not, please let me know. However, all of the controls that are returned have an empty text.
The code can be used as follows:
var foregroundWindow = new WinCEControl(GetForegroundWindow()); // working properly
Assert.That("The Window Title", foregroundWindow.Text); // working properly
Assert.That(manorMenu.TextPresent("Text to find")); // not working although /
// "Text to find" is a value within the control tree of the window.
As for the name, I do not even know how to retrieve it at all. So far my searching was unsuccessful.
public class WinCEControl
{
[DllImport("coredll.dll", SetLastError = true)]
private static extern IntPtr GetWindow(IntPtr hWnd, uint uCmd);
[DllImport("coredll.dll", EntryPoint = "SendMessage", CharSet = CharSet.Auto)]
private static extern bool SendMessage(IntPtr hWnd, uint Msg, int wParam, StringBuilder lParam);
private const int WM_GETTEXT = 0x000D;
private const uint GW_CHILD = 5;
private const uint GW_HWNDLAST = 1;
private const uint GW_HWNDNEXT = 2;
public WinCEControl(IntPtr handle)
{
this.Handle = handle;
}
public IntPtr Handle { get; private set; }
public string Text
{
get
{
var stringBuilder = new StringBuilder(256);
SendMessage(this.Handle, WM_GETTEXT, stringBuilder.Capacity, stringBuilder);
return stringBuilder.ToString();
}
}
public IEnumerable<WinCEControl> Children()
{
var childHandle = GetWindow(Handle, GW_CHILD);
if (childHandle == IntPtr.Zero)
{
yield break;
}
var lastHandle = GetWindow(childHandle, GW_HWNDLAST);
while (childHandle != lastHandle)
{
yield return new WinCEWindow(childHandle);
childHandle = GetWindow(childHandle, GW_HWNDNEXT);
}
yield return new WinCEWindow(lastHandle);
}
public IEnumerable<WinCEControl> DescendantControls()
{
var nodes = new Queue<WinCEControl>(new[] { this });
while (nodes.Any())
{
var node = nodes.Dequeue();
if (node != this)
{
yield return node;
}
foreach (var n in node.Children()) nodes.Enqueue(n);
}
}
public bool TextPresent(string text)
{
foreach (var descendantControl in DescendantControls())
{
if (descendantControl.Text == text)
{
return true;
}
}
return false;
}
}
My goal is to be able to perform UI tests against a running application on the CE device. If there is a solid C# library to achieve the same which works on Windows CE I am very hear.
Update: As mentioned in my comment I have failed to find a library or framework for automating foreign WinForms processes on the Win CE. I tried the "simple-wince-gui-automation" and it fails to retrieve the texts, too.

Pinvoke ONLY code for getting proccess via its name

as i was trying to have a test and learn about native p/invoke functions i was trying to use only pinvoke and then compare the time it takes to get process info with .net simple
Process myProc = Process.GetProcessByName("WinRAR");
though i feel that i need to realy measure that almost 2 pages in length code, using P/invoke just so i could get same results, but this time ONLY with native code, i guess that it should be faster and i want to atleast get to benchmark both ,so please help here .
so it seems that my code is 1) ... ok i guess i could count to 20
"enumerating" all it's issues, but mainly :
it doesn't enumerate all processes for a strange reason i did not see winrar for instance
second it is far from being as short as pinvoke bunche-of-methods needs
(i am using Winforms app, though you could hard code the ProcessName needed in order to "search" for the correct process)
most of comments here is by the author of well, most parts of the code
i only modified it a little to have enum later so you could choose between searching via window title or process name
so this is the code:
main entry - create instance of class :
pinvokers Pi = new pinvokers();
// Find all Internet Explorer instances(i used winrar, as my second task in this project is also test application performance... later on, and again, using only native calls)
Pi.FindWindows(0, pinvokers.SearchWin.ProcName, null, new Regex(TBX_SelectedWinName.Text), new pinvokers.FoundWindowCallback(pinvokers.foundWindowToPrint));
public class pinvokers
{
// Win32 constants.
const int WM_GETTEXT = 0x000D;
const int WM_GETTEXTLENGTH = 0x000E;
[DllImport("user32.Dll")]
private static extern Boolean EnumChildWindows(int hWndParent, PChildCallBack lpEnumFunc, int lParam);
[DllImport("user32.Dll")]
private static extern int GetWindowText(int hWnd, StringBuilder text, int count);
[DllImport("user32.Dll")]
private static extern int GetWindowThreadProcessId(int hWnd, out int lpdwProcessId);
[DllImport("user32.Dll")]
private static extern Int32 SendMessage(int hWnd, int Msg, int wParam, StringBuilder lParam);
[DllImport("user32.Dll")]
private static extern Int32 SendMessage(int hWnd, int Msg, int wParam, int lParam);
[DllImport("kernel32.dll")]
public static extern IntPtr OpenProcess(int dwDesiredAccess, bool bInheritHandle, int dwProcessId);
[DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
static extern uint GetWindowModuleFileName(IntPtr hwnd,
StringBuilder lpszFileName, uint cchFileNameMax);
[DllImport("psapi.dll")]
private static extern uint GetModuleFileNameEx(IntPtr hWnd, IntPtr hModule, StringBuilder lpFileName, int nSize);
// The PChildCallBack delegate that we used with EnumWindows.
private delegate bool PChildCallBack(int hWnd, int lParam);
// This is an event that is run each time a window was found that matches the search criterias. The boolean
// return value of the delegate matches the functionality of the PChildCallBack delegate function.
static event FoundWindowCallback foundWindowCB;
public delegate bool FoundWindowCallback(int hWnd);
int parentHandle;
Regex process;
#region <<=========== not nedded - search by window title. i am looking to search via process name ===========>>
/* <- commented all unsuesd
Regex windowText;
public static bool foundWindowToPrint(int handle)
{
// Print the window info.
printWindowInfo(handle);
// Continue on with next window.
return true;
}
static void printWindowInfo(int handle)
{
// Get the text.
int txtLength = SendMessage(handle, WM_GETTEXTLENGTH, 0, 0);
StringBuilder sbText = new StringBuilder(txtLength + 1);
SendMessage(handle, WM_GETTEXT, sbText.Capacity, sbText);
// Now we can write out the information we have on the window.
MessageBox.Show("Handle: " + handle);
MessageBox.Show("Text : " + sbText);
}
=====>end of un needed search bywindowtitle1
*/
#endregion
// my plan was to use enum instead of if !empty or null value for ither title name or process name so that's how the original code ditermin wich one to execute.
public enum SearchWin
{
Title, ProcName
}
//first method (and that's all i could really tell.. as it is full of callbacks and private extern, and delegates ... so complex
public void FindWindows(int parentHandle, SearchWin By, Regex windowText, Regex process, FoundWindowCallback fwc)
{
this.parentHandle = parentHandle;
//this.windowText = windowText;
this.process = process;
// Add the FounWindowCallback to the foundWindow event.
foundWindowCB = fwc;
// Invoke the EnumChildWindows function.
EnumChildWindows(parentHandle, new PChildCallBack(enumChildWindowsCallback), 0);
}
// This function gets called each time a window is found by the EnumChildWindows function. The foun windows here
// are NOT the final found windows as the only filtering done by EnumChildWindows is on the parent window handle.
private bool enumChildWindowsCallback(int handle, int lParam)
{
#region <<=========== not nedded - search by window title. #2 ===========>>
/* <--here too window title portion of code commented
// If a window text was provided, check to see if it matches the window.
if (windowText != null)
{
int txtLength = SendMessage(handle, WM_GETTEXTLENGTH, 0, 0);
StringBuilder sbText = new StringBuilder(txtLength + 1);
SendMessage(handle, WM_GETTEXT, sbText.Capacity, sbText);
// If it does not match, return true so we can continue on with the next window.
if (!windowText.IsMatch(sbText.ToString()))
return true;
}
*/
#endregion //endr2
// If a process name was provided, check to see if it matches the window.
if (process != null)
{
int processID;
GetWindowThreadProcessId(handle, out processID);
// Now that we have the process ID, we can use the built in .NET function to obtain a process object.
var ProcessName = GetProcNameByID(processID);
// If it does not match, return true so we can continue on with the next window.
if (!process.IsMatch(ProcessName))
return true;
}
// If we get to this point, the window is a match. Now invoke the foundWindow event and based upon
// the return value, whether we should continue to search for windows.
return foundWindowCB(handle);
}
private string GetProcNameByID(int ProcID)
{
IntPtr hProcess = OpenProcess(0x0410, false, ProcID);
StringBuilder text = new StringBuilder(1000);
GetWindowModuleFileName(hProcess, text, (uint)text.Capacity);
//GetModuleFileNameEx(hProcess, IntPtr.Zero, text, text.Capacity);
//CloseHandle(hProcess); here i am trying to catch what enumeration of windows got in its net , all this code does work just copy and paste it .
var t = text.ToString();
if (t.ToLower().Contains("inra"))
MessageBox.Show(t);
return t;
}
}
so could this be a little shorter is a side question
main one is :
Why does it not enumerate all the processes ?

i don't know if it is the best i could get or maybe someone who knows what he is doing with win api, or p/invoke or if i had to try and make unmanagedLand win over .net built in calsses
i might have rolled my sleeves and put some c++ code together (will probbably take another week)
and compile it to a dll to get all functions together in one DLL (should it do some perfomance gain)
and then i might have cut some gap .
(by the way now it is much closer to system diagnostic results thogh i thought it will be much faster and i was wrong)
but still it was only for knowing i am safe to use .net C#
and to trust microsoft for knowing much better than me (: how to make a good proggraming language.
this is the code i was using to make it through all those dllllls import. i should have known that import anything and it costs( here it might be the import tax that is costely)
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void But_StartPinvoke_Click(object sender, EventArgs e)
{
var userInputOK = TBX_SelectedProcessName.userInput();
if(!userInputOK)
MessageBox.Show(RApss.mesgs.EmptyTbx);
RApss.Strings.UserInput = TBX_SelectedProcessName.Text;
RApss.Globs.TbxPname = TBX_SelectedProcessName.Text.AddSufixEXE();
doWarmUp();
Stopwatch SwGpbn = Stopwatch.StartNew();
SwGpbn.Start();
//string _netProcName = Process.GetProcessesByName(RApss.Strings.UserInput)[0].ProcessName;
Process p = Process.GetProcessesByName(RApss.Strings.UserInput)[0];
if (p.ProcessName.ResultFetched())
SwGpbn.Stop();
var msElps_Net4 = SwGpbn.ElapsedMilliseconds;
SwGpbn.Reset();
SwGpbn.Start();
EnumProcessesV3.GetProcessByName();
SwGpbn.Stop();
var msElpsNat = SwGpbn.ElapsedMilliseconds;
SwGpbn.Reset();
SwGpbn.Reset();
if (RApss.Globs.Result.ResultFetched()) MessageBox.Show(string.Concat(RApss.Globs.Result, "\r\nWas Fetched In: ", msElpsNat, " Via PinVoke\r\n Was Fetched In: ", msElps_Net4," Via C#.NET !" ));
}
private void doWarmUp()
{
List<string> swarm = new List<string>();
for (int i = 0; i < 50000; i++)
{
swarm.Add((i + 1 *500).ToString());
}
}
}
public class RApss
{
public class Globs
{
public static string TbxPname;
public static string Result = string.Empty;
}
public class Strings
{
public static string intputForProcessName = "Requiered Process Name";
public static string UserInput = string.Empty;
}
public class mesgs
{
public static string EmptyTbx = string.Concat("please fill ", Strings.intputForProcessName, " field");
}
}
public class EnumProcessesV3
{
#region APIS
[DllImport("psapi")]
private static extern bool EnumProcesses(
[MarshalAs(UnmanagedType.LPArray, ArraySubType = UnmanagedType.U4)] [In][Out] IntPtr[] processIds,
UInt32 arraySizeBytes,
[MarshalAs(UnmanagedType.U4)] out UInt32 bytesCopied);
[DllImport("kernel32.dll")]
static extern IntPtr OpenProcess(ProcessAccessFlags dwDesiredAccess, [MarshalAs(UnmanagedType.Bool)] bool bInheritHandle, IntPtr dwProcessId);
[DllImport("kernel32.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool CloseHandle(IntPtr hObject);
[DllImport("psapi.dll")]
static extern uint GetModuleFileNameEx(IntPtr hProcess, IntPtr hModule, [Out] StringBuilder lpBaseName, [In] [MarshalAs(UnmanagedType.U4)] int nSize);
[DllImport("psapi.dll", SetLastError = true)]
public static extern bool EnumProcessModules(IntPtr hProcess,
[Out] IntPtr lphModule,
uint cb,
[MarshalAs(UnmanagedType.U4)] out uint lpcbNeeded);
[DllImport("psapi.dll")]
static extern uint GetModuleBaseName(IntPtr hProcess, IntPtr hModule, [Out] StringBuilder lpBaseName, [In] [MarshalAs(UnmanagedType.U4)] int nSize);
#endregion
#region ENUMS
[Flags]
enum ProcessAccessFlags : uint
{
All = 0x001F0FFF,
Terminate = 0x00000001,
CreateThread = 0x00000002,
VMOperation = 0x00000008,
VMRead = 0x00000010,
VMWrite = 0x00000020,
DupHandle = 0x00000040,
SetInformation = 0x00000200,
QueryInformation = 0x00000400,
Synchronize = 0x00100000
}
#endregion
public static void GetProcessByName()
{
UInt32 arraySize = 120;
UInt32 arrayBytesSize = arraySize * sizeof(UInt32);
IntPtr[] processIds = new IntPtr[arraySize];
UInt32 bytesCopied;
bool success = EnumProcesses(processIds, arrayBytesSize, out bytesCopied);
#region <<=========== some cleanUps ============>>
// trying to check what could have been taking extra mssssnds
//Console.WriteLine("success={0}", success);
//Console.WriteLine("bytesCopied={0}", bytesCopied);
//if (!success)
//{
// MessageBox.Show("Boo!");
// return;
//}
//if (0 == bytesCopied)
//{
// MessageBox.Show("Nobody home!");
// return;
//}
#endregion
UInt32 numIdsCopied = bytesCopied >> 2;
#region <<===========same here commenting anything that might cost nerowing the options ============>>
//if (0 != (bytesCopied & 3))
//{
// UInt32 partialDwordBytes = bytesCopied & 3;
// MessageBox.Show(String.Format("EnumProcesses copied {0} and {1}/4th DWORDS... Please ask it for the other {2}/4th DWORD",
// numIdsCopied, partialDwordBytes, 4 - partialDwordBytes));
// return;
//}
//taking initialisation of SB out of loop was a winning thought but nada no change maybe in nanos
#endregion
for (UInt32 index = numIdsCopied; index> 1 ; index--) // reversing from last process id(chitting) to erlier process id did not help to win the contest
{
StringBuilder szProcessName = new StringBuilder(1000);
int x = szProcessName.Capacity;
string sName = PrintProcessName(processIds[index-1],szProcessName,x);
if (sName.Equals(RApss.Globs.TbxPname)) // tryng hardcoded value instead of reading from a variable.(GlobalsClass)
{
RApss.Globs.Result = sName;
break;
}
////////IntPtr PID = processIds[index];
////////Console.WriteLine("Name '" + sName + "' PID '" + PID + "'");
}
}
static string PrintProcessName(IntPtr processID, StringBuilder sb, int Cpcty)
{
string sName = "";
//bool bFound = false;
IntPtr hProcess = OpenProcess(ProcessAccessFlags.QueryInformation | ProcessAccessFlags.VMRead, false, processID);
if (hProcess != IntPtr.Zero)
{
IntPtr hMod = IntPtr.Zero;
uint cbNeeded = 0;
EnumProcessModules(hProcess, hMod, (uint)Marshal.SizeOf(typeof(IntPtr)), out cbNeeded);
if (GetModuleBaseName(hProcess, hMod, sb, Cpcty) > 0)
{
sName = sb.ToString();
//bFound = true;
}
// Close the process handle
CloseHandle(hProcess);
}
//if (!bFound)
//{
// sName = "<unknown>";
//}
return sName;
}
}
}
namespace RExt
{
public static class UserInputs
{
public static bool userInput(this TextBox tbxId)
{
return tbxId.Text.Length > 1;
}
}
public static class strExt
{
public static bool ResultFetched(this string StrToCheck)
{
return !string.IsNullOrWhiteSpace(StrToCheck);
}
public static string AddSufixEXE(this string StrToAppendEXE)
{
return string.Concat(StrToAppendEXE, ".exe");
}
}
}
if thats not working, make sure the project is targeting x86 CPU and Rebuild
for some reason i did not check what is needed to make it suit both x64 & x86

Using AttachConsole, user must hit enter to get regular command line

I have a progaram that can be ran both as a winform, or from command line. If it is invoked from a command line I call AttachConsole(-1) to attach to parent console.
However, after my program ends, the user must hit enter to get back the standard command prompt ("c:\>"). is there a way to avoid that need?
Thanks.
I could wrap it in a cmd file to avoid that issue, but I would like to do it from my exe.

Try adding this line just before your exe exits...
System.Windows.Forms.SendKeys.SendWait("{ENTER}");
Bit of a hack, but best I could find when I encountered that problem.

Here is the safest hack that solves the Enter key problem regardless of whether the console window is in the foreground, background, or minimized. You can even run it in multiple console windows.
using System;
using System.Runtime.InteropServices;
using System.Threading;
using System.Windows.Forms;
namespace WindowsAndConsoleApp
{
static class Program
{
const uint WM_CHAR = 0x0102;
const int VK_ENTER = 0x0D;
[DllImport("kernel32.dll")]
static extern bool AttachConsole(int dwProcessId);
private const int ATTACH_PARENT_PROCESS = -1;
[DllImport("kernel32.dll", SetLastError = true)]
static extern bool FreeConsole();
[DllImport("kernel32.dll")]
static extern IntPtr GetConsoleWindow();
[DllImport("user32.dll")]
static extern int SendMessage(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam);
[STAThread]
static void Main(string[] args)
{
if (args.Length > 0)
{
// Do this first.
AttachConsole(ATTACH_PARENT_PROCESS);
Console.Title = "Console Window - Enter Key Test";
Console.WriteLine("Getting the handle of the currently executing console window...");
IntPtr cw = GetConsoleWindow();
Console.WriteLine($"Console handle: {cw.ToInt32()}");
Console.WriteLine("\nPut some windows in from of this one...");
Thread.Sleep(5000);
Console.WriteLine("Take your time...");
Thread.Sleep(5000);
Console.WriteLine("Sending the Enter key now...");
// Send the Enter key to the console window no matter where it is.
SendMessage(cw, WM_CHAR, (IntPtr)VK_ENTER, IntPtr.Zero);
// Do this last.
FreeConsole();
}
else
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new MainForm());
}
}
}
}

Rob L's approach is somewhat dangerous as it will send an Enter to the active window. A better approach is to actual send the Enter to the correct process (console).
here is how
internal static class NativeMethods
{
[DllImport("kernel32.dll", SetLastError = true)]
internal static extern bool AllocConsole();
[DllImport("kernel32.dll", SetLastError = true)]
internal static extern bool FreeConsole();
[DllImport("kernel32", SetLastError = true)]
internal static extern bool AttachConsole(int dwProcessId);
[DllImport("user32.dll")]
internal static extern IntPtr GetForegroundWindow();
[DllImport("user32.dll", SetLastError = true)]
internal static extern uint GetWindowThreadProcessId(IntPtr hWnd, out int lpdwProcessId);
[DllImport("User32.Dll", EntryPoint = "PostMessageA")]
internal static extern bool PostMessage(IntPtr hWnd, uint msg, int wParam, int lParam);
internal const int VK_RETURN = 0x0D;
internal const int WM_KEYDOWN = 0x100;
}
--snip--
bool attached = false;
// Get uppermost window process
IntPtr ptr = NativeMethods.GetForegroundWindow();
int u;
NativeMethods.GetWindowThreadProcessId(ptr, out u);
Process process = Process.GetProcessById(u);
if (string.Compare(process.ProcessName, "cmd", StringComparison.InvariantCultureIgnoreCase) == 0)
{
// attach to the current active console
NativeMethods.AttachConsole(process.Id);
attached = true;
}
else
{
// create new console
NativeMethods.AllocConsole();
}
Console.Write("your output");
NativeMethods.FreeConsole();
if (attached)
{
var hWnd = process.MainWindowHandle;
NativeMethods.PostMessage(hWnd, NativeMethods.WM_KEYDOWN, NativeMethods.VK_RETURN, 0);
}
This solution is build upon the code that is found here:
http://www.jankowskimichal.pl/en/2011/12/wpf-hybrid-application-with-parameters/

It's late to the party and there have been many suggestions over the years, but as I recently just solved this issue myself by stitching together a bunch of information from various posts, I thought I'd post the solution here since it has the most relevant title.
This solution works without using the Enter key or simulating a key press. The only thing I couldn't completely solve is intercepting the Enter from the parent console when your application starts. I think this is impossible because it happens before you get a chance to intercept it; however, there is a reasonable quasi-workaround.
Before diving into the code, here's the sequence of things we need to do:
Attach to the parent console
Capture the text of the current prompt output by the parent console
Clear the parent console's prompt by overwriting it with spaces (not sure it's possible to otherwise prevent this from happening)
Interact with the console as normal
Restore parent console's previous prompt by writing what we captured in #2
This is what it would look like in use:
using System;
using System.Windows.Forms;
public static void Main(string[] args)
{
if (args.Length > 0)
{
using (new ConsoleScope())
{
Console.WriteLine("I now own the console");
Console.WriteLine("MUA HA HA HA HA HA!!!");
}
}
else
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new MainForm());
}
}
... and now for the code. It's more than I'd like, but this is as succinct as I could make it for a post. May this help others attempting the same thing. Enjoy!
using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Text;
public sealed class ConsoleScope : IDisposable
{
const int ATTACH_PARENT_PROCESS = -1;
const int STD_OUTPUT_HANDLE = -11;
readonly bool createdNewConsole;
readonly string prompt;
bool disposed;
public ConsoleScope()
{
if (AttachParentConsole())
{
prompt = CaptureParentConsoleCurrentPrompt();
}
else
{
AllocConsole();
createdNewConsole = true;
}
}
~ConsoleScope() => CleanUp();
public void Dispose()
{
CleanUp();
GC.SuppressFinalize(this);
}
static string CaptureParentConsoleCurrentPrompt()
{
var line = (short)Console.CursorTop;
var length = (short)Console.CursorLeft;
var noPrompt = line == 0 && length == 0;
if (noPrompt)
{
return default;
}
return ReadCurrentLineFromParentConsoleBuffer(line, length);
}
static string ReadCurrentLineFromParentConsoleBuffer(short line, short length)
{
var itemSize = Marshal.SizeOf(typeof(CHAR_INFO));
var buffer = Marshal.AllocHGlobal(length * itemSize);
var encoding = Console.OutputEncoding;
var text = new StringBuilder(capacity: length + 1);
var coordinates = default(COORD);
var textRegion = new SMALL_RECT
{
Left = 0,
Top = line,
Right = (short)(length - 1),
Bottom = line,
};
var bufferSize = new COORD
{
X = length,
Y = 1,
};
try
{
if (!ReadConsoleOutput(GetStdOutputHandle(), buffer, bufferSize, coordinates, ref textRegion))
{
Marshal.ThrowExceptionForHR(Marshal.GetHRForLastWin32Error());
}
var array = buffer;
for (var i = 0; i < length; i++)
{
var info = Marshal.PtrToStructure<CHAR_INFO>(array);
var chars = encoding.GetChars(info.CharData);
text.Append(chars[0]);
array += itemSize;
}
}
finally
{
Marshal.FreeHGlobal(buffer);
}
// now that we've captured the current prompt, overwrite it with spaces
// so that things start where the parent left off at
Console.SetCursorPosition(0, line);
Console.Write(new string(' ', length));
Console.SetCursorPosition(0, line - 1);
return text.ToString();
}
void CleanUp()
{
if (disposed)
{
return;
}
disposed = true;
RestoreParentConsolePrompt();
if (createdNewConsole)
{
FreeConsole();
}
}
void RestoreParentConsolePrompt()
{
var text = prompt;
if (!string.IsNullOrEmpty(text))
{
// this assumes the last output from your application used
// Console.WriteLine or otherwise output a CRLF. if it didn't,
// you may need to add an extra line here
Console.Write(text);
}
}
[StructLayout(LayoutKind.Sequential)]
struct CHAR_INFO
{
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 2)]
public byte[] CharData;
public short Attributes;
}
[StructLayout(LayoutKind.Sequential)]
struct COORD
{
public short X;
public short Y;
}
[StructLayout(LayoutKind.Sequential)]
struct SMALL_RECT
{
public short Left;
public short Top;
public short Right;
public short Bottom;
}
// REF: https://learn.microsoft.com/en-us/windows/console/allocconsole
[DllImport("kernel32.dll", SetLastError = true)]
static extern bool AllocConsole();
// REF: https://learn.microsoft.com/en-us/windows/console/attachconsole
[DllImport("kernel32.dll", SetLastError = true)]
static extern bool AttachConsole(int dwProcessId);
// REF: https://learn.microsoft.com/en-us/windows/console/freeconsole
[DllImport("kernel32.dll", SetLastError = true)]
static extern bool FreeConsole();
static bool AttachParentConsole() => AttachConsole(ATTACH_PARENT_PROCESS);
// REF: https://learn.microsoft.com/en-us/windows/console/readconsoleoutput
[DllImport("kernel32.dll", SetLastError = true)]
static extern bool ReadConsoleOutput(IntPtr hConsoleOutput, IntPtr lpBuffer, COORD dwBufferSize, COORD dwBufferCoord, ref SMALL_RECT lpReadRegion);
[DllImport("kernel32.dll", SetLastError = true)]
static extern IntPtr GetStdHandle(int nStdHandle);
static IntPtr GetStdOutputHandle() => GetStdHandle(STD_OUTPUT_HANDLE);
}

Ok, I don't have the solution, but it seems to be because the cmd.exe is not waiting on the started process, whereas with a normal console application cmd.exe waits until the the application exits. I don't know what makes cmd.exe decide to wait or not on an application, normal Windows Forms applications are just started and cmd.exe doesn't wait for it to exit. Maybe this hint triggers somebody! I will dig a bit deeper in the mean while.

Try calling the FreeConsole function prior to exiting your executable.

This one has been the easiest solution for me:
myapp.exe [params] | ECHO.

I attempted my own Qt cpp version of Chris Martinez's C# answer:
https://github.com/NightVsKnight/QtGuiConsoleApp/blob/main/QtGuiConsoleApp/main.cpp
#include <QApplication>
#include <QMessageBox>
#ifdef Q_OS_WIN
// Solution posted to https://stackoverflow.com/a/73942013/252308
#define VC_EXTRALEAN
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
QString consolePromptClear()
{
QString prompt = nullptr;
auto bSuccess = AttachConsole(ATTACH_PARENT_PROCESS);
if (bSuccess)
{
auto hStdOut = GetStdHandle(STD_OUTPUT_HANDLE);
if (hStdOut != INVALID_HANDLE_VALUE)
{
CONSOLE_SCREEN_BUFFER_INFO csbi;
bSuccess = GetConsoleScreenBufferInfo(hStdOut, &csbi);
if (bSuccess)
{
auto dwConsoleColumnWidth = (DWORD)(csbi.srWindow.Right - csbi.srWindow.Left + 1);
auto xEnd = csbi.dwCursorPosition.X;
auto yEnd = csbi.dwCursorPosition.Y;
if (xEnd != 0 || yEnd != 0)
{
DWORD dwNumberOfChars;
SHORT yBegin = yEnd;
{
// Walk backwards to find first all blank line
auto pBuffer = (LPWSTR)LocalAlloc(LPTR, dwConsoleColumnWidth * sizeof(WCHAR));
while (yBegin)
{
COORD dwReadCoord = { 0, yBegin };
bSuccess = ReadConsoleOutputCharacterW(hStdOut, pBuffer, dwConsoleColumnWidth, dwReadCoord, &dwNumberOfChars);
if (!bSuccess) break;
DWORD i;
for (i=0; i < dwNumberOfChars; ++i)
{
WCHAR wchar = pBuffer[i];
if (wchar != L' ')
{
--yBegin;
break;
}
}
if (i == dwNumberOfChars)
{
// Found all blank line; we want the *next* [non-blank] line
yBegin++;
break;
}
}
LocalFree(pBuffer);
}
auto promptLength = (yEnd - yBegin) * dwConsoleColumnWidth + xEnd;
auto lpPromptBuffer = (LPWSTR)LocalAlloc(LPTR, promptLength * sizeof(WCHAR));
COORD dwPromptCoord = { 0, yBegin };
bSuccess = ReadConsoleOutputCharacterW(hStdOut, lpPromptBuffer, promptLength, dwPromptCoord, &dwNumberOfChars);
if (bSuccess)
{
Q_ASSERT(promptLength == dwNumberOfChars);
prompt = QString::fromWCharArray(lpPromptBuffer, dwNumberOfChars);
bSuccess = SetConsoleCursorPosition(hStdOut, dwPromptCoord);
if (bSuccess)
{
FillConsoleOutputCharacterW(hStdOut, L' ', promptLength, dwPromptCoord, &dwNumberOfChars);
}
}
LocalFree(lpPromptBuffer);
}
}
}
}
if (prompt.isEmpty())
{
FreeConsole();
return nullptr;
}
else
{
freopen_s((FILE**)stdout, "CONOUT$", "w", stdout);
freopen_s((FILE**)stderr, "CONOUT$", "w", stderr);
freopen_s((FILE**)stdin, "CONIN$", "r", stdin);
return prompt;
}
}
void consolePromptRestore(const QString& prompt)
{
if (prompt.isEmpty()) return;
auto hStdOut = GetStdHandle(STD_OUTPUT_HANDLE);
if (hStdOut == INVALID_HANDLE_VALUE) return;
CONSOLE_SCREEN_BUFFER_INFO csbi;
BOOL bSuccess = GetConsoleScreenBufferInfo(hStdOut, &csbi);
if (!bSuccess) return;
auto xEnd = csbi.dwCursorPosition.X;
auto yEnd = csbi.dwCursorPosition.Y;
if (xEnd == 0 && yEnd == 0) return;
auto buffer = prompt.toStdWString();
auto lpBuffer = buffer.data();
auto nLength = (DWORD)buffer.length();
COORD dwWriteCoord = { 0, (SHORT)(yEnd + 1) };
DWORD dwNumberOfCharsWritten;
WriteConsoleOutputCharacterW(hStdOut, lpBuffer, nLength, dwWriteCoord, &dwNumberOfCharsWritten);
dwWriteCoord = { (SHORT)dwNumberOfCharsWritten, (SHORT)(yEnd + 1) };
SetConsoleCursorPosition(hStdOut, dwWriteCoord);
}
#else
// Non-Windows impl...
#endif
int main(int argc, char *argv[])
{
// NOTE: Any console output before call to consolePromptClear() may get cleared.
// NOTE: Console vs GUI mode has **NOTHING** to do with being passed arguments; You can easily pass arguments to GUI apps.
int returnCode;
auto prompt = consolePromptClear();
if (prompt.isEmpty())
{
QApplication a(argc, argv);
a.setQuitOnLastWindowClosed(true);
QMessageBox msgBox(nullptr);
msgBox.setWindowTitle(a.applicationName());
msgBox.setTextFormat(Qt::RichText);
msgBox.setText("App is detected to be running as a GUI");
msgBox.setStandardButtons(QMessageBox::Ok);
msgBox.show();
returnCode = a.exec();
}
else
{
QCoreApplication a(argc, argv);
QTextStream qout(stdout);
qout << "App is detected to be running as a Console" << Qt::endl;
returnCode = 0;
consolePromptRestore(prompt);
}
return returnCode;
}