private void ReadFiles(string path)
        {
            try
            {
                Stream stream = new FileStream(path,FileMode.Open);
                FileInfo fileinfo = new FileInfo(path);
                string fileExtension = fileinfo.Extension.ToUpper();

                if (fileExtension.Equals(".RTF"))
                {
                    this.textBox1.LoadFile(stream, RichTextBoxStreamType.RichText);

（c:\users\ibm_admin\documents\visual studio 2010\Projects\CS_TEST_APP_002\Form1.cs(230,35): error CS1061: 'System.Windows.Forms.TextBox' does not contain a definition for 'LoadFile' and no extension method 'LoadFile' accepting a first argument of type 'System.Windows.Forms.TextBox' could be found (are you missing a using directive or an assembly reference?)）（这个错误是怎么回事啊）
                }
                else
                {
                    this.textBox1.LoadFile(stream, RichTextBoxStreamType.PlainText);
                }
                    

                stream.Close();
            }
            catch { return; }
        }