Kill Excel Process Programmatically

Kill all excels in process..VB.net

Private Declare Function GetWindowThreadProcessId Lib "user32" (ByVal hWnd As Integer, ByRef lpdwProcessId As IntPtr) As IntPtr
Dim xlapp As New excel.Application
    .
    .
Dim processId1 As IntPtr
GetWindowThreadProcessId(xlapp.Hwnd, processId1)
Dim excelProcess1 As Process = Process.GetProcessById(processId1.ToInt32())
Debug.WriteLine(processId1)
excelProcess1.Kill()
xlapp = Nothing
GC.Collect()
GC.WaitForPendingFinalizers()