public partial class UserControl1 : UserControl,IObjectSafety
    {        
        [DllImport("testdll.dll")]
        public static extern int TestWnd(string frequency, string duration);

        private void button1_Click(object sender, EventArgs e)
        {
            this.label1.Text = getstr();
        }

        private string getstr()
        {
            return TestWnd("sdf", "sdsdfs").ToString();
        }
    }

testdll.dll是用C++编写的.
但单击button1时,怎么出现两个MessageBox对话框呢?
MessageBox对话框里面的内容就是我传过去的两个参数的值sdf,sdsdfs.是怎么回事啊?