How do I get the classname of the active window?

By using this code I can get the title of the active window..

    [DllImport("user32.dll")]
static extern IntPtr GetForegroundWindow();

[DllImport("user32.dll")]
static extern int GetWindowText(IntPtr hWnd, StringBuilder text, int count);

private string GetActiveWindowTitle()
{
    const int nChars = 256;
    IntPtr handle = IntPtr.Zero;
    StringBuilder Buff =开发者_如何学JAVA new StringBuilder(nChars);
    handle = GetForegroundWindow();

    if (GetWindowText(handle, Buff, nChars) > 0)
    {
        return Buff.ToString();
    }
    return null;

But how should I do to get the classname of the active window?

Simply pinvoke GetClassName(). This returns the Windows class name for a window, it doesn't have anything to do with a C# class. Getting the C# class name for a window in another process is not possible. Take a look at the Managed Spy++ tool for possible hacks if this is a Winforms app.

I expanded Hans Passant's answer into working code:

Usage:

string className = Spy.GetForegroundWindowClassName();

Class:

using System.Runtime.InteropServices;
using System.Text;

public static class Spy
{
    [DllImport("user32.dll")]
    private static extern IntPtr GetForegroundWindow();

    [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
    private static extern int GetClassName(IntPtr hWnd, StringBuilder lpClassName, int nMaxCount);

    public static string GetForegroundWindowClassName()
    {
        IntPtr hWnd = GetForegroundWindow();
        var className = new StringBuilder(256);
        GetClassName(hWnd, className, className.Capacity);
        return className.ToString();
    }
}

Side Note: in my case, I just needed a basic utility to tell me the class name of a window so I could reference that in my C# code. After writing the code above, I realized I could achieve the same thing using pre-existing utilities. One such utility I see mentioned often in the C# community is Visual Studio's Spy++ tool. I didn't bother trying that since it requires downloading 2.5 GB of C++ components. Instead, I used the "Window Spy" tool that comes with Autohotkey. Autohotkey is a tiny download compared to what's needed for Spy++, so I think it's a good option if it suits your needs.