如果不用线程可以!
         private void button3_Click(object sender, System.EventArgs e)
         {
          Form selectIntType=new SelectIntType(); selectIntType.MdiParent=App.frm;
         selectIntType.Show();
         this.Close();
          }
----------------------------------------------
用了线程就不可以了?
private void button3_Click(object sender, System.EventArgs e)
{
this.labMsg.Text="正在解压资源文件请等待...";
System.Threading.Thread thrCompress = new               System.Threading.Thread(new ThreadStart(startInt)); 
thrCompress.Start();
button3.Enabled=false;
}     private void startInt()
         {
          Form selectIntType=new SelectIntType(); selectIntType.MdiParent=App.frm;
         selectIntType.Show();
         this.Close();
          }