Develop Reference

Geany, Linux, C#, MySql.Data, NOT Visual Studio; the using statement doesn't compile

I just got C# working on Ubutnu. It's all good. But now I want MySql too. I installed the gacutil, and downloaded the connector, and I ran the gacutil, which it seemed like it worked.
I'm using Geany as my ide for now. It's free and already installed, and it worked great; until I tried to add using MySql.Data; I've read through all the stackoverflow posts for MySql.Data: they all state that I need to add an entry to my reference list in the VS project. Well, I don't have a reference list, nor a project. My 'project' directory only contains two(2) files: Test.cs, and Test.exe. MySql.Data is registered in the gac! Arg! Please, how do I get this working?!?!?
Running the gacutil:
dysmondad#Julep:/etc/mono/mysql/v4.5$ sudo gacutil -i MySql.Data.dll
Installed MySql.Data.dll into the gac (/usr/lib/mono/gac)
Complete source code for testing Mono install.
using System;
using System.Collections;
using System.Collections.Generic;
using MySql.Data; // <- this isn't recognized.
public class Test
{
static public void Main ()
{
List<int> integers = new List<int>();
integers.Add(7);
integers.Add(14);
integers.Add(21);
foreach( int i in integers )
{
Console.WriteLine(i);
}
}
}
UPDATE-1: Just found this on the MySql support page._______
You are now ready to compile your application. You must ensure that when you compile your application you include the Connector/Net component using the -r: command-line option. For example:
shell> gmcs -r:System.dll -r:System.Data.dll -r:MySql.Data.dll HelloWorld.cs
But...these don't work
-r:MySql.Data.dll
--nor--
-r:MySql.Data
UPDATE-2: I just discovered that if I use the -r option, and include the full path and name of the dll (even though it was registered with the gacutil) that seems to satisfy the compiler. So now my question is: how to get it to work with just the package name and not have to specify the full path?

The type or namespace name 'SQLConnection' could not be found

Something seems wrong with the c# database for Accounts:
Right at the database I get the error message of:
Error 1 The type or namespace name 'Connection' could not be found
(are you missing a using directive or an assembly reference?)
What am I possibly doing wrong with it? I would like to connect to the database in the Accounts
Code 1:
public void setCustAccounts(String custId) {
SQLConnection connect = acctsConnect();
Command statement = null;
ResultSet result = null;
String sql = "SELECT acctNo FROM Accounts Where Cid = '" + custId + "';";
try{
statement = connect.createStatement();
result = statement.executeQuery(sql);
while (result.next()){
result.getRow();
Account acct = new Account(result.getString("acctNo"));
custAccounts.add(acct);
}
}
finally {
connect.close();
}
}
code:-
public SQLConnection acctsConnect(){
try{
Class.forName("C:\\ChattBankMDB.mdb");
}catch(ClassNotFoundException e){
Console.WriteLine("Error: " + e);
}
SQLConnection connect = null;
try{
connect = DriverManager.getConnection("C:\\ChattBankMDB.mdb");
}catch(SQLException e){
Console.WriteLine("Error: " + e);
}
return connect;
}
}
}

using System.Data.SqlClient;
Along with the above line we need to also check if the actual system assembly reference is there or not. In my case I had the directive but assembly reference was missing.
To add assembly we can do the following.
Browse dll file for SqlClient in and add it.
--or--- simpler way is to install nuget package.
Right Click on Project > Manage Nuget Packages > Search & install 'System.Data.SqlClient'
Make sure it is compatible with the type of project (Core/Standard);

You are missing the using Directive statement in your code.
using System.Data.SqlClient;

Right Click on your project file in the solution panel, and then
Click on the Manage NuGet Packages option.
In the NuGet Package Manager window, Select the Browser Tab. Search for
System.Data.SqlClient and Press enter
Select the first option, System.Data.SqlClient by Microsoft Click on the install button
Wait for the installation to complete. Done.
Source YouTube Video: SqlConnection could not be found in the namespace | Fixed

As Community Ans says, you should install the NuGet package in your project first. If you don't, Visual Studio's Intellisense will still work when you add the using but you won't be able to use it's types in your code.

I had the same problem and I found the solution shown above.
Instead of using SQLiteConnection(YourPath), use :
var db = new SQLite.SQLiteConnection(DataBasePath);
db.CreateTable<YourTable>();

The solution is to Install and use the new System.Data.SqlClient package in NuGet to your project or solution. Follow these steps to install the package.
Right Click on your solution from the solution panel in VS.
From the context menu, select the Manage NuGet Packages for solutions...
In the NuGet Package Manager window, select the Browse Tab.
In the search box type in System.Data.SqlClient and press enter.
Look for the package System.Data.SqlClient by Microsoft and select it.
A small panel will open at the right side of the window with the list of projects in your solution. Select only the projects you want the SqlClient package to be installed.
Then press the install button. Wait for the installation to complete. NuGet will install the selected package and all it’s dependencies.
Now go back to your solution or project and rebuild. You will not get the error again.

The package reference can be added via the .NET CLI:
dotnet add package System.Data.SqlClient

So for me, VS2022, I had the latest Nuget package and using statement in my project. I deleted the using statement, then went back to the SqlConnection statement in my code, moused over the SqlConnection object, clicked on Show Potential Fixes, clicked on using Microsoft.Data.SqlClient; and it fixed it.
HTH...

You can must remove before all SqlConnection, Sql... code blocks.
After package install and write code.
VS to suggest using System.Data.SqlClient...

System.Web.HttpUtility.UrlEncode c# using

In the following code:
for (int line = 0; line < CHUNKSTOBEFOUND; line++) {
nvc.Add ("search", System.Web.HttpUtility.UrlEncode (stringsToSearchFor[line]));
}
I get told namespace name HttpUtility does not exist.
http://msdn.microsoft.com/en-us/library/system.web.httputility.aspx seems to indicate I should use System.Web. I've tried using that, but I STILL get the error. Is there something else I'm supposed to include or use?

As competent_said, you are probably targeting the Client Profile in your project, in which System.Web.dll is not available. You can target the full framework in Project Properties to get it back working.
Another possible cause could be that you are not referencing System.Web library. To do so:
Right click the "Reference" in the Solution Explorer.
Choose "Add Reference"
Check the ".NET" tab is selected.
Search for, and add "System.Web".
Maybe you are just missing an using directive using System.Web; on the top of your source file.

You are most likely using the Client Profile version of the .Net framework. You need to open your project properties and change the framework version to the full version.

Windows Store Project - Assembly reference error when trying to run cmd commands from a C# file in VS2012

I'm doing some exercises with C# in the trial version of VS 2012. I want to execute a cmd command from a CS file. For this, I've tried Process.Start as well as System.Diagnostics.Process that are mentioned in these posts:
Run Command Prompt Commands
Execute CMD command from code
However, despite I added "using System.Diagnostics" and "using System.ComponentModel", I'm still getting "The type or namespace name 'Process' does not exist in the namespace 'System.Diagnostics', missing assembly reference" error. ¿Any suggestion so I can i get rid of this error? Thanks in advance.

This usually happens when you have Target framework = .NET Framework Client Profile, but DLL you reference is from .NET Framework (full). Make sure you have System.dll in your references from valid framework.
I just did the same - created empty console application with the following code:
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.ComponentModel;
using System.Linq;
using System.Text;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
var prc = Process.Start("explorer.exe");
}
}
}
Works perfectly fine for me.
Additional thing to check is Intellisense - when you start typing "System.Diagnostics.Proc"... - does it show you dropdown with "Process" there?
UPDATE:
Windows Store projects are based on different version of target .NET Framework - .NET for Windows Store apps, which does not support functionality you need.
For more details do web search:".NET for Windows Store apps". Helpful links:
http://msdn.microsoft.com/en-us/library/windows/apps/br230302.aspx
http://msdn.microsoft.com/en-us/library/windows/apps/br230232.aspx

ManagementObject Class not showing up in System.Management namespace

I'm trying to write some WMI in my windows form and the ManagementObject is givin me the
"The type or namespace name 'ManagementObject' could not be found" Error
Here is my un-complete code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Threading;
using System.Security.Policy;
using System.Management;
using System.Management.Instrumentation;
namespace ConsoleApplication2
{
class Program
{
static void Main(string[] args)
{
ManagementObject disk = new ManagementObject("Win32_LogicalDisk.DeviceID=\"C:\"");

Right-click References on the right and manually add System.Management. Even though I included it in the using statement I still had to do this. Once I did, all worked fine.

Have you added a reference to the System.Management assembly?

In Solution Explorer, right click on References, then Add Reference ... and under Framework, you should activate the System.Management framework.

You need to add a reference to System.Management.dll to your project.
You can see System.Management.Instrumentation without adding a reference to System.Management.dll because it is included in a different library (System.Core.dll, which is included as a reference automatically), but you cannot access the other types contained by that namespace without explicitly adding a reference to the System.Management.dll library.

~ just add System.management using nuget manager,
It worked for me! c#

I think the problem is there is no WMI object for Win32_LogicalDisk.DeviceID=\"C:\".
Try to replace:
ManagementObject disk = new ManagementObject("Win32_LogicalDisk.DeviceID=\"C:\"");
with:
ManagementObject disk = new ManagementObject("Win32_LogicalDisk");
and then to step through each field:
foreach (ManagementObject o in disk.Get()){
//Do what ever you need here.... For example:
Console.WriteLine(o.ToString());
}

Make sure your project isn't set up to compile against the .NET 4 Framework Client Profile.
Please see Namespace not recognized (even though it is there) for more details.

The version of Visual Studio that I have does not import ManagementObjectSearcher by importing "System.Management" namespace. If you have the same issue, try adding a reference to "System.Management.dll' by doing the following steps.
Click on project properties on solution explorer in Visual Studio.
Go to "References".
Click on "Add" to add a new reference.
Click on "Browse...".
Navigate to "C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727".
Add a reference to "C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\System.Management.dll".

This is quite an old post but I just had to troubleshoot this. The only way I got it working with Visual Basic 2022 was to download and install through the NuGet Installer. Manually adding the .dll did not work for me. Once NuGet Manager is open Search: System.Management and download the latest from Microsoft, hope this helps someone.