关于修改TextBox中的文本(winform)

        Action<string, TextBox> actionAddTxtDelegate = (x, y) => 
        {
            y.AppendText(x.ToString() + "\r\n");
            y.ScrollToCaret();
        };


        Action<string, TextBox> actionUpdateTxtDelegate = (x, y) =>
        {
            string[] lines = y.Lines;
            if (lines.Length > 0)
            {
                lines[lines.Length - 2] = x;
            }
            y.Lines = lines;
            y.ScrollToCaret();
        };    

        public void UpdateTxt(string txt)
        {
              this.textBox1.BeginInvoke(actionUpdateTxtDelegate,txt,this.textBox1);
        }        

         public void AddTxt(string txt)
        {
              this.textBox1.BeginInvoke(actionAddTxtDelegate ,txt,this.textBox1);
        }