C# Signature:

[DllImport("user32.dll", CharSet=CharSet.Auto)]
static extern IntPtr FindWindow(string lpClassName, string lpWindowName);

VB Signature:

Declare Auto Function FindWindow Lib "user32" (ByVal lpClassName As String, _
    ByVal lpWindowName As String) As IntPtr

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

Tips & Tricks:

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

Sample Code:

//C#
//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 fsuck? 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

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