#region 退格删除
        /// <summary>
        /// 退格删除
        /// </summary>
        private void backSpace()
        {
            if (this.tempStr.Length > 0)
            {
                this.tempStr = this.tempStr.Remove(this.tempStr.Length - 1);
                this.txtMsg.Text = tempStr;
            }

        }
        #endregion

------解决方案--------------------
实在不行用win API, sendinput, sendmessage 之类

------解决方案--------------------
txtContent.Text = txtContent.Text.SubString(0, txtContent.Text.Length - 1);

------解决方案--------------------
探讨

txtContent.Text = txtContent.Text.SubString(0, txtContent.Text.Length - 1);


------解决方案--------------------

哦。。。
if (txtContent.SelectStart != 0)
{
   int pos = txtContent.SelectStart;
   txtContent.Text = txtContent.Text.SubString(0, txtContent.SelectStart - 1) + txtContent.Text.SubString(txtContent.SelectStart + txtContent.SelectLength);
   textContent.SelectStart = pos - 1;
}

------解决方案--------------------
把光标处的字符删了不就相当于退格了么。