C# Signature:

// [DllImport("coredll.dll"), SetLastError = true)] //<-- Use this insead of user32.dll for Windows Mobile
[DllImport("user32.dll", SetLastError = true)]
static extern IntPtr FindWindow(string lpClassName, string lpWindowName);

VB Signature:

    <DllImport("user32.dll", SetLastError:=True, CharSet:=CharSet.Auto)> _
    Private Shared Function FindWindow(ByVal lpClassName As String, ByVal lpWindowName As String) As IntPtr
    End Function

    <DllImport("user32.dll", EntryPoint:="FindWindow", SetLastError:=True, CharSet:=CharSet.Auto)> _
    Private Shared Function FindWindowByClass(ByVal lpClassName As String, ByVal zero As IntPtr) As IntPtr
    End Function

    <DllImport("user32.dll", EntryPoint:="FindWindow", SetLastError:=True, CharSet:=CharSet.Auto)> _
    Private Shared Function FindWindowByCaption(ByVal zero As IntPtr, ByVal lpWindowName As String) As IntPtr
    End Function

User-Defined Types:

None.

Notes:

The FindWindow function retrieves the handle to the top-level window whose class name and window name match the specified strings. This function does not search child windows.

Works hand-in-hand with FindWindowEx

*If lpClassName is NULL FindWindow will search for the window by the lpWindowName (window's title) only. This is useful if the class of a particular window is variable.

Tips & Tricks:

Use the fantastic Spy++ (One of the vStudio tools) to get details of specific Windows you're looking for.

Sample Code (C#):

        public static int FindWindow(string windowName, bool wait)
        {
            int hWnd = FindWindow(null, windowName);
            while (wait && hWnd == 0)
            {
                System.Threading.Thread.Sleep(500);
                hWnd = FindWindow(null, windowName);
            }

            return hWnd;
        }

        // THE FOLLOWING METHOD REFERENCES THE SetForegroundWindow API
        public static bool BringWindowToTop(string windowName, bool wait)
        {
            int hWnd = FindWindow(windowName, wait);
            if (hWnd != 0)
            {
                return SetForegroundWindow((IntPtr)hWnd);
            }
            return false;
        }

Sample Code (VB.net):

//Open Up blank Notepad First !
string lpszParentClass = "Notepad";
string lpszParentWindow = "Untitled - Notepad";
string lpszClass = "Edit";

IntPtr ParenthWnd = new IntPtr(0);
IntPtr hWnd = new IntPtr(0);
ParenthWnd = FindWindow(lpszParentClass,lpszParentWindow);
if (ParenthWnd.Equals(IntPtr.Zero))  
     Console.WriteLine("Notepad Not Running");
else
{
     hWnd = FindWindowEx(ParenthWnd,hWnd,lpszClass,"");
     if (hWnd.Equals(IntPtr.Zero))  
     Console.WriteLine("What the F??? Notepad doesn't have an edit component ?");
     else
     {
     Console.WriteLine("Notepad Window: " + ParenthWnd.ToString());
     Console.WriteLine("Edit Control: " + hWnd.ToString());
     }
}

'// VB (chellios at gmail dot com)
'// Open up a blank Notepad!
Dim lpszParentClass As String = "Notepad"
Dim lpszParentWindow As String = "Untitled - Notepad"
Dim lpszClass As String = "Edit"

Dim ParenthWnd As New IntPtr(0)
Dim hWnd As New IntPtr(0)

ParenthWnd = FindWindow(lpszParentClass, lpszParentWindow)

If ParenthWnd.Equals(IntPtr.Zero) Then
    Debug.WriteLine("Notepad Not Running!")
Else
    hWnd = FindWindowEx(ParenthWnd, hWnd, lpszClass, "")

    If hWnd.Equals(IntPtr.Zero)
       Debug.WriteLine("What the F??? Notepad doesn't have an Edit component, how strange.")
    Else
       Debug.WriteLine("Notepad Window: " & ParenthWnd.ToString())
       Debug.WriteLine("Edit Control: " & hWnd.ToString())
    End If
End If

Alternative Managed API:

Do you know one? Please contribute it!

'If you are using VB.net in Visual Studio 2005, don't forget "Imports System.Runtime.InteropServices" at the top of your

'module or none of this beautiful code will work at all

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