Can't import User32.dll into Visual Studio

Question

I tried:

To add user32.dll from Reference Manager, and imported it from Windows\System32\user32.dll, I got Error Message:

A reference to 'C:\Windows\System32\user32.dll couldn't be added. Please make sure that the file is accessible, and that it is a valid assembly or COM component.
using System.Runtime.InteropServices; [DllImport("user32")]
To launch Visual Studio as Administrator

Nothing works... it goes on my nerves I am trying 2 hours to import this damn .dll...

What is your actual goal of adding that DLL? You've mentioned `DllImport` which clearly doesn't need adding native DLL as reference... — Alexei Levenkov, Jul 28 '13 at 20:11
@RohitVats: That question deals with .NET or COM DLLs, not plain Win32 DLLs like `user32.dll`. — RichieHindle, Jul 28 '13 at 20:13

score 11 · Accepted Answer · answered Jul 28 '13 at 20:14

11

You do not need to add a reference to User32.dll. It is part of Windows and can be imported in your code without adding a reference. You do this using P/Invoke.

[System.Runtime.InteropServices.DllImport("user32.dll")]
public static extern void SetWindowText(int hWnd, String text);

private void button3_Click(object sender, EventArgs e)
{
    IntPtr wHnd = this.Handle;//assuming you are in a C# form application
    SetWindowText(wHnd.ToInt32(), "New Window Title");
}

See Also:

answered Jul 28 '13 at 20:14

jrbeverly

1,611
14
20

Thank you! I didn't realize/know that method should be defined ( public static extern void SetWindowText(int hWnd, String text); ) – jovanMeshkov Jul 28 '13 at 20:23
Well it is not that method purely that needs to be defined. Each method that you reference from `user32.dll` must be present in that format: `[System.Runtime.InteropServices.DllImport("user32.dll")]` `public static extern void ();` – jrbeverly Jul 28 '13 at 21:15

score 1 · Answer 2 · answered Jul 28 '13 at 20:14

1

It's not a .NET dll. You don't "add reference" the same way you do with .NET dlls. Instead you have to add P/Invoke code to your app to invoke the functions you want. Here's a good resource for learning pinvoke: http://pinvoke.net/

answered Jul 28 '13 at 20:14

Dax Fohl

10,654
6
46
90

Can't import User32.dll into Visual Studio

2 Answers2

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