[vb.net]判断窗体是否已打开

if my.Application.OpenForms.Item("FormName") isnot nothing then搜索
do something here
else
do something here 
end if 

Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare Function IsWindowVisible Lib "user32" (ByVal hwnd As Long) As Long
Private Declare Function IsIconic Lib "user32" Alias "IsIconic" (ByVal hwnd As Long) As Long
相关的使用示例：
Dim I As Long, J As Long, K As Long
I = FindWindow(vbNullString, "我的程序")
‘I为0表示“我的程序”没有运行，否则它是程序的句柄
J = IsWindowVisible(I)
‘J－－如窗口可见则返回TRUE（非零）
K = IsIconic(I)
‘判断窗口是否已最小化,非零表示成功，零表示失败

        Dim myProcesses As System.Diagnostics.Process() = System.Diagnostics.Process.GetProcessesByName("TrackRecorder")
        If myProcesses.Length > 1 Then
            MessageBox.Show("TrackRecorder.exe has run.")
            Windows.Forms.Application.Exit()
        End If