I've got a Windows Form program that creates a Config object which contains various configuration variables used by my program.
Within the main form, it contains a button to open a new configuration form, where it passes the Config object as a reference -
FormConfig button = new FormConfig(ref config);
button.ShowDialog();
Now in the FormConfig class, I can access the Config object within the main constructor
public FormConfig(ref Config config)
{
InitializeComponent();
// can access config.xyz OK here
}
However within the new form, I've got a button that calls another function that needs to access the reference Config object, however I'm struggling to find a clean way to do so.
I can create another Config object as part of the FormConfig class, and then copy the referenced Config to it in the main constructor, however then the original config object doesn't get updated.
How can I achieve this?
PS apologies in advance if this is already answered, but my searches have so far failed to find a solution, possibly because I'm not sure what the correct search terms should be.
And the solution thanks to #cmos, is to declare the Config class as static, which negates the need to use any referencing or passing objects between classes/functions -
public static class Config
{
public static bool SettingA = true;
}
Which means I can access and modify the Config object from anywhere within the same namespace with the following code, without needing to have a class instance -
Config.SettingA
Thanks to all those who helped point me in the right direction.
ASP.NET has specicial application folders like App_Code which:
Contains source code for shared classes and business objects (for example, ..cs, and .vb files) that you want to compile as part of your application. In a dynamically compiled Web site project, ASP.NET compiles the code in the App_Code folder on the initial request to your application. Items in this folder are then recompiled when any changes are detected.
Problem is, I'm building a web application, not a dynamically compiled web site. But I'd love to be able to store config values directly in C#, rather than serve via an XML and have to read in during Application_Start and store in HttpContext.Current.Application
So I have the following code in /App_Code/Globals.cs:
namespace AppName.Globals
{
public static class Messages
{
public const string CodeNotFound = "The entered code was not found";
}
}
Which could be anywhere within the application like this:
string msg = AppName.Globals.Messages.CodeNotFound;
The goal is to be able to store any literals in a configurable area that can be updated without recompiling the entire application.
I can use the .cs file by setting its build action to compile, but doing so strips out App_Code/Globals.cs from my output.
Q: Is there a way to identify some parts of a project that should dynamically compile while allowing the rest of the project to be precompiled?
If I set the build action to content - the .cs file will get copied to the bin folder and compiled at runtime. However, in that case, it's not available at design time.
If I set the build action to compile - I can access the objects the same as any other compiled class during design/runtime, but it'll get stripped out of the /App_Code folder when published. I can still place it in the output directory via Copy Always, but the already compiled classes seem to take priority so I can't push config changes without re-deploying the whole application.
Problem Overview
We need to overcome two different problems here:
The first is having a single file that can be compiled at build time and also re-compiled at runtime.
The second is resolving the two different versions of that class created by the solving the first problem so we can actually make use of them.
Problem 1 - Schrödinger's Compilation
The first problem is trying to get a class that is both compiled and not compiled. We need to compile it at design time so that other sections of code are aware it exists and can use its properties with strong typing. But normally, compiled code is stripped out of the output so there aren't multiple versions of the same class causing naming conflicts.
In any case, we need to compile the class initially, but there are two options to persist a re-compilable copy:
Add the file to App_Code, which is compiled at runtime by default, but set it's Build Action = Compile so it's available at design time as well.
Add a regular class file, which is compiled at design time by default, but set it to Copy to Output Directory = Copy Always, so there's a chance we can evaluate it at runtime as well.
Problem 2 - Self Imposed DLL Hell
At a bare minimum, this is a tricky task to charge to the compiler. Any code that consumes a class, must have a guarantee that it exists at compile time. Anything that is dynamically compiled, whether via App_Code or otherwise, will be part of an entirely different assembly. So producing an identical class is treated more like a picture of that class. The underlying type might be the same, but ce n'est une pipe.
We have two options: use an interface or crosswalk between assemblies:
If we use an interface, we can compile it with the initial build and any dynamic types can implement that same interface. This way we are safely relying on something that exists at compile time, and our created class can be safely swapped out as a backing property.
If we cast types across assemblies, it's important to note that any existing usages rely on the type that was originally compiled. So we'll need to grab the values from the dynamic type and apply those property values to the original type.
Existing Answers
Per evk, I like the idea of querying AppDomain.CurrentDomain.GetAssemblies() on startup to check for any new assemblies/classes. I'll admit that using an interface is probably an advisable way to unify precompiled/dynamically compiled classes, but I would ideally like to have a single file/class that can simply be re-read if it changes.
Per S.Deepika, I like the idea of dynamically compiling from a file, but don't want to have to move the values to a separate project.
Ruling out App_Code
App_Code does unlock the ability to build two versions of the same class, but it's actually hard to modify either one after publication as we'll see. Any .cs file located in ~/App_Code/ will be dynamically compiled when the application runs. So in Visual Studio, we can build the same class twice by adding it to App_Code and setting the Build Action to Compile.
Build Action and Copy Output:
When we debug locally, all .cs files will be built into the project assembly and the physical file in ~/App_Code will also be built as well.
We can identify both types like this:
// have to return as object (not T), because we have two different classes
public List<(Assembly asm, object instance, bool isDynamic)> FindLoadedTypes<T>()
{
var matches = from asm in AppDomain.CurrentDomain.GetAssemblies()
from type in asm.GetTypes()
where type.FullName == typeof(T).FullName
select (asm,
instance: Activator.CreateInstance(type),
isDynamic: asm.GetCustomAttribute<GeneratedCodeAttribute>() != null);
return matches.ToList();
}
var loadedTypes = FindLoadedTypes<Apple>();
Compiled and Dynamic Types:
This is really close to solving problem #1. We have access to both types every time the app runs. We can use the compiled version at design time and any changes to the file itself will automatically be recompiled by IIS into a version that we can access at runtime.
The problem is apparent however once we step out of debug mode and try to publish the project. This solution relies on IIS building the App_Code.xxxx assembly dynamically, and that relies on the .cs file being inside the root App_Code folder. However, when a .cs file is compiled, it is automatically stripped out of the published project, to avoid the exact scenario we're trying to create (and delicately manage). If the file was left in, it would produce two identical classes, which would create naming conflicts whenever either one was used.
We can try to force its hand by both compiling the file into the project's assembly and also copying the file into the output directory. But App_Code doesn't work any of it's magic inside of ~/bin/App_Code/. It'll only work at the root level ~/App_Code/
App_Code Compilation Source:
With every publish, we could manually cut and paste the generated App_Code folder from the bin and place it back at the root level, but that's precarious at best. Perhaps we could automate that into build events, but we'll try something else...
Solution
Compile + (Copy to Output and Manually Compile File)
Let's avoid the App_Code folder because it will add some unintended consequences.
Just create a new folder named Config and add a class that will store the values we want to be able to modify dynamically:
~/Config/AppleValues.cs:
public class Apple
{
public string StemColor { get; set; } = "Brown";
public string LeafColor { get; set; } = "Green";
public string BodyColor { get; set; } = "Red";
}
Again, we'll want to go to the file properties (F4) and set to compile AND copy to output. This will give us a second version of the file we can use later.
We'll consume this class by using it within a static class that exposes the values from anywhere. This helps separate concerns, especially between the need to dynamically compile and statically access.
~/Config/GlobalConfig.cs:
public static class Global
{
// static constructor
static Global()
{
// sub out static property value
// TODO magic happens here - read in file, compile, and assign new values
Apple = new Apple();
}
public static Apple Apple { get; set; }
}
And we can use it like this:
var x = Global.Apple.BodyColor;
What we'll attempt to do inside the static constructor, is seed Apple with the values from our dynamic class. This method will be called once every time the application is restarted, and any changes to the bin folder will automatically trigger recycling the app pool.
In short order, here's what we'll want to accomplish inside of the constructor:
string fileName = HostingEnvironment.MapPath("~/bin/Config/AppleValues.cs");
var dynamicAsm = Utilities.BuildFileIntoAssembly(fileName);
var dynamicApple = Utilities.GetTypeFromAssembly(dynamicAsm, typeof(Apple).FullName);
var precompApple = new Apple();
var updatedApple = Utilities.CopyProperties(dynamicApple, precompApple);
// set static property
Apple = updatedApple;
fileName - The File path might be specific to where you'd like to deploy this, but note that inside of a static method, you need to use HostingEnvironment.MapPath instead of Server.MapPath
BuildFileIntoAssembly - In terms of loading the assembly from a file, I've adapted the code from the docs on CSharpCodeProvider and this question on How to load a class from a .cs file. Also, rather than fight dependencies, I just gave the compiler access to every assembly that was currently in the App Domain, same as it would have gotten on the original compilation. There's probably a way to do that with less overhead, but it's a one time cost so who cares.
CopyProperties - To map the new properties onto the old object, I've adapted the method in this question on how to Apply properties values from one object to another of the same type automatically? which will use reflection to break down both objects and iterate over each property.
Utilities.cs
Here's the full source code for the Utility methods from above
public static class Utilities
{
/// <summary>
/// Build File Into Assembly
/// </summary>
/// <param name="sourceName"></param>
/// <returns>https://msdn.microsoft.com/en-us/library/microsoft.csharp.csharpcodeprovider.aspx</returns>
public static Assembly BuildFileIntoAssembly(String fileName)
{
if (!File.Exists(fileName))
throw new FileNotFoundException($"File '{fileName}' does not exist");
// Select the code provider based on the input file extension
FileInfo sourceFile = new FileInfo(fileName);
string providerName = sourceFile.Extension.ToUpper() == ".CS" ? "CSharp" :
sourceFile.Extension.ToUpper() == ".VB" ? "VisualBasic" : "";
if (providerName == "")
throw new ArgumentException("Source file must have a .cs or .vb extension");
CodeDomProvider provider = CodeDomProvider.CreateProvider(providerName);
CompilerParameters cp = new CompilerParameters();
// just add every currently loaded assembly:
// https://stackoverflow.com/a/1020547/1366033
var assemblies = from asm in AppDomain.CurrentDomain.GetAssemblies()
where !asm.IsDynamic
select asm.Location;
cp.ReferencedAssemblies.AddRange(assemblies.ToArray());
cp.GenerateExecutable = false; // Generate a class library
cp.GenerateInMemory = true; // Don't Save the assembly as a physical file.
cp.TreatWarningsAsErrors = false; // Set whether to treat all warnings as errors.
// Invoke compilation of the source file.
CompilerResults cr = provider.CompileAssemblyFromFile(cp, fileName);
if (cr.Errors.Count > 0)
throw new Exception("Errors compiling {0}. " +
string.Join(";", cr.Errors.Cast<CompilerError>().Select(x => x.ToString())));
return cr.CompiledAssembly;
}
// have to use FullName not full equality because different classes that look the same
public static object GetTypeFromAssembly(Assembly asm, String typeName)
{
var inst = from type in asm.GetTypes()
where type.FullName == typeName
select Activator.CreateInstance(type);
return inst.First();
}
/// <summary>
/// Extension for 'Object' that copies the properties to a destination object.
/// </summary>
/// <param name="source">The source</param>
/// <param name="target">The target</param>
/// <remarks>
/// https://stackoverflow.com/q/930433/1366033
/// </remarks>
public static T2 CopyProperties<T1, T2>(T1 source, T2 target)
{
// If any this null throw an exception
if (source == null || target == null)
throw new ArgumentNullException("Source or/and Destination Objects are null");
// Getting the Types of the objects
Type typeTar = target.GetType();
Type typeSrc = source.GetType();
// Collect all the valid properties to map
var results = from srcProp in typeSrc.GetProperties()
let targetProperty = typeTar.GetProperty(srcProp.Name)
where srcProp.CanRead
&& targetProperty != null
&& (targetProperty.GetSetMethod(true) != null && !targetProperty.GetSetMethod(true).IsPrivate)
&& (targetProperty.GetSetMethod().Attributes & MethodAttributes.Static) == 0
&& targetProperty.PropertyType.IsAssignableFrom(srcProp.PropertyType)
select (sourceProperty: srcProp, targetProperty: targetProperty);
//map the properties
foreach (var props in results)
{
props.targetProperty.SetValue(target, props.sourceProperty.GetValue(source, null), null);
}
return target;
}
}
But Why Tho?
Okay, so there are other more conventional ways to accomplish the same goal. Ideally, we'd shoot for Convention > Configuration. But this provides the absolute easiest, most flexible, strongly typed way to store config values I've ever seen.
Normally config values are read in via an XML in an equally odd process that relies on magic strings and weak typing. We have to call MapPath to get to the store of value and then do Object Relational Mapping from XML to C#. Instead here, we have the final type from the get go, and we can automate all of the ORM work between identical classes that just happen to be compiled against different assemblies.
In either case, the dream output of that process is to be able to write and consume C# directly. In this case, if I want to add an extra, fully configurable property, it's as easy as adding a property to the class. Done!
It will be available immediately and recompiled automatically if that value changes without needing to publish a new build of the app.
Dynamically Changing Class Demo:
Here's the full, working source code for the project:
Compiled Config - Github Source Code | Download Link
You can move configuration part to separate project, and create common interface like (IApplicationConfiguration.ReadConfiguration) to access it.
You can compile the code dynamically at run time like below, and you can access the configuration details using reflection.
public static Assembly CompileAssembly(string[] sourceFiles, string outputAssemblyPath)
{
var codeProvider = new CSharpCodeProvider();
var compilerParameters = new CompilerParameters
{
GenerateExecutable = false,
GenerateInMemory = false,
IncludeDebugInformation = true,
OutputAssembly = outputAssemblyPath
};
// Add CSharpSimpleScripting.exe as a reference to Scripts.dll to expose interfaces
compilerParameters.ReferencedAssemblies.Add(Assembly.GetExecutingAssembly().Location);
var result = codeProvider.CompileAssemblyFromFile(compilerParameters, sourceFiles); // Compile
return result.CompiledAssembly;
}
Let's see how dynamic compilation of files in App_Code works. When first request to your application arrives, asp.net will compile code files in that folder into assembly (if were not compiled before), and then load that assembly into current application domain of asp.net application. That's why you see your message in a watch - assembly was compiled and is available in current app domain. Because it was compiled dynamically, of course you have compile-time error when trying to reference it explicitly - this code is not yet compiled, and when it will be compiled - it might have completely different structure and message you reference might just not be there at all. So there is no way you can explicitly reference code from dynamic-generated assembly.
What options do you have then? For example, you can have an interface for your messages:
// this interface is located in your main application code,
// not in App_Code folder
public interface IMessages {
string CodeNotFound { get; }
}
Then, in your App_Code file - implement that interface:
// this is in App_Code folder,
// you can reference code from main application here,
// such as IMessages interface
public class Messages : IMessages {
public string CodeNotFound
{
get { return "The entered code was not found"; }
}
}
And then in main application - provide a proxy by searching current app domain for assembly with type that implements IMessage interface (only once, then cache it) and proxy all calls to that type:
public static class Messages {
// Lazy - search of app domain will be performed only on first call
private static readonly Lazy<IMessages> _messages = new Lazy<IMessages>(FindMessagesType, true);
private static IMessages FindMessagesType() {
// search all types in current app domain
foreach (var asm in AppDomain.CurrentDomain.GetAssemblies()) {
foreach (var type in asm.GetTypes()) {
if (type.GetInterfaces().Any(c => c == typeof(IMessages))) {
return (IMessages) Activator.CreateInstance(type);
}
}
}
throw new Exception("No implementations of IMessages interface were found");
}
// proxy to found instance
public static string CodeNotFound => _messages.Value.CodeNotFound;
}
This will achieve your goal - now when you change code in App_Code Messages class, on next request asp.net will tear down current application domain (first waiting for all pending requests to finish), then create new app domain, recompile your Messages and load into that new app domain (note that this recreating of app domain always happen when you change something in App_Code, not just in this particular situation). So next request will already see new value of your message without you explicitly recompile anything.
Note that you obviously cannot add or remove messages (or change their names) without recompiling main application, because doing that will require changes to IMessages interface which belongs to main application code. If you try - asp.net will throw compilation failure error on next (and all subsequent) requests.
I'd personally avoid doing such things, but if you are fine with that - why not.
VS2012 for desktop .net framework 4.5 normal windows forms applications, not WPF
Hello, I tried to search for an answer, but I'm not sure of the correct terminology. I've managed to break my code, and can't understand what I've done wrong. (i didn't think i had changed anything, but ...)
I have a solution which contains 2 projects. The first project is an executable program, and the second is a DLL, which is loaded at run time and used by the first project.
the first project contains a form, and a static class with public static strings in the same namespace. (and some other unconnected classes). specifically:
namespace project1_namespace
{
static class settings
{
public static string some_words = "some words in a string";
}
class dll_callback{
//.. some public methods here
}
dll_callback dllcallback; // instance is initialised in the code (not shown)
Form form;
public partial class frm_splash : Form
{
private void frm_splash_FormClosing(object sender, FormClosingEventArgs e)
{
// this function actually loads the DLL, ensuring its the last step
//... some error checking code removed for brevity
Assembly assembly = Assembly.LoadFrom("c:\dllpath\project2.dll");
Type type_init = assembly.GetType("project2_class");
object init = Activator.CreateInstance(type_init, form, dllcallback);
//... some error checking code removed for brevity
}// end method
}// end form class
}// end namespace
when the form is closing, the method shown above is called which calls the second projects class project2_class constructor.
in project 2, the DLL, there is:
namespace project2_namespace
{
// how did i get this working to reference "settings" class from project 1??
public class project2_class
{
public project2_class(project2_namespace.Form1 form_ref, object callback)
{
settings.some_words = "the words have changed";
//... some more stuff
}
}
}
Now, i was experimenting with some code in an entirely different part of project2, and VS2012 suddenly started refusing to compile stating:
error CS0103: The name 'settings' does not exist in the current context
the standard solution to this appears to be to add a reference to project2, but that would create circular dependencies because project 1 calls 2 as a DLL.
I really honestly don't think i had changed anything relevant to this, but also clearly I have.
looking at it, i cant see how project 2 would have access to a class in project 1 without a reference, but the list of arguments to the project2_class constructor doesn't include one, and I am absolutely positive that it hasn't changed (and I cant change it for backwards compatibility reasons).
would really appreciate help with this, as its been a lot of work to get this working.
as a side note, I've definitely learned my lesson about not using source control. and not making "how this works" comments instead of "what this does" comments.
may dynamic help you? You can not get the setting string at complie time.
I'm using C# ASP.NET VS2010.
I have a procedure on an .aspx.cs that reads a XML file and works just fine.
It goes like this:
string fileName = "~/App_Data/" + filename + ".xml";
DataSet ds = new DataSet();
ds.ReadXml(MapPath(fileName));
I use this procedure alot to read various files with minimal changes (the file name), therefore, I tried to put the procedure in a Class1.cs file (in the App_Code folder), but I get this error message:
The type or namespace name 'MapPath' does not exist in the namespace 'Microsoft.SqlServer.Server' (are you missing an assembly reference?)
I use this MapPath to read an XML file into a dataset this way:
ds.ReadXml(Server.MapPath(fileName));
The filename is a string variable declared a few lines earlier:
string fileName = "~/App_Data/" + inputString + ".xml";
After putting this line in the class.cs file, the VS2010 asked to resolve the missing Server by replacing it into Microsoft.SqlServer.Server locally (at the same line and not by adding a namespace) , so the line in it's new form looks like this:
ds.ReadXml(Microsoft.SqlServer.Server.MapPath(fileName));
For the record, I made sure that all namespaces on the source .aspx.cs file are at the class file.
Why the difference between the Class1.cs and the .aspx.cs?
How do I workaround this?
What should I change in order to read the XML file from this new class file?
Is there a replacement for my line to read the XML file into the dataset?
MapPath is method of the System.Web.HttpServerUtility class, you need an instance of this class to call the method. In ASP pages, an instance is available in the Server member of the Page; elsewhere, you'll have to supply it. Either as
HttpContext.Current.Server.MapPath(fileName);
which uses the Server variable for the current HttpContext if you're inside one. HttpContext class contains many HTTP-related objects that you're used to access through Page members - like Request, Response, Server. The Current static property gives the context for the request you're currently handling. Inside classes in App_Code folder of your ASP web project, you're safe to assume that there's an active context.
If you wanted to move your class to a separate assembly, it would be better to make the Server (or Context) a parameter of your method and make it the responsibility of the caller to supply one:
public class Class1
{
public void MyMethod(HttpServerUtility server)
{
//...
server.MapPath(fileName);
//...
}
}
From the ASP page it would then be called like class1instance.MyMethod(this.Server);
Microsoft.SqlServer.Server has nothing to do with it, only the class/member names are the same and Visual Studio got it wrong.
If I define a class in a file
~/App_Code/Extensions/MyExtension/MyClass.cs
Is it possible to retrieve the filename by type (or 'MyExtension' part of it) without hard coding it?
var extTypes = getExtensions();
foreach(var extType in extTypes)
{
// something like
var files = extType.GetSourceFiles();
//or maybe asp.net keeps track of types in the dynamically created assembly
var files2 = SomeAspNetClass.WhereDidThisTypeComeFrom(extType);
}
Or inject it to the class in any way?
[ThisFile]
public class MyClass : MyBase
{
private string _file = <thisfile>;
}
This sort of information is only really available in compiled languages (like C#) when you have debugging symbols included. So if you had a Debug build then you could get at this information by examining the current StackFrame.
var stackFrame = new StackFrame(true);
stackFrame.GetFileName()
Of course you probably don't want to have debug builds on your production code, so it may be worth-while looking at alternate ways to achieve whatever it is your trying to do here.
maybe you are looking for this?
Assembly.GetAssembly(typeof(YourTypeHere)).Location