设置SelectionStart 属性，例如
        private void textBox1_MouseClick(object sender, MouseEventArgs e)
        {
            textBox1.SelectionStart = 1;
        }

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http://topic.csdn.net/t/20040726/15/3211168.html

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不用吧。。本来就是指到哪里点到哪里的。。你看看是不是还有别的事件加载。。

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用的到的，好

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C# code
public void textBoxEmpty_Validating(object sender, CancelEventArgs e) 
        { 
            TextBox tb = (TextBox)sender; 
            if (tb.Text.Length == 0) 
            { 
                tb.BackColor = Color.Red; 
                tb.Tag = false; 
                // e.Cancel = true; 
            } 
            else 
            { 
                tb.BackColor = System.Drawing.SystemColors.Window; 
                tb.Tag = true; 
            } 
            validateOK(); 

        } 

        public void textBox_TextChanged(object sender, EventArgs e) 
        { 
            TextBox tb = (TextBox)sender; 

            if (tb.Text.Length == 0) 
            { 
                tb.BackColor = Color.Red; 
                tb.Tag = false; 
                //e.Cancel = true; 
            } 

            else 
            { 
                tb.BackColor = System.Drawing.SystemColors.Window; 
                tb.Tag = true; 
            } 
            validateOK(); 

        }

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validateOK();里面是啥？