使用.Trim()应注意的问题：
请看以下代码
protected void Button1_Click(object sender, EventArgs e)
{
string str = "abc ";
str.Trim();
TextBox1.Text = str;
string str2 = "abc ";
TextBox2.Text = str2.Trim();
}
执行结果：
TextBox1里仍然有空格
TextBox2里没有空格
protected void Button1_Click(object sender, EventArgs e)
{
string str = "abc ";
str.Trim();
TextBox1.Text = str;
TextBox2.Text = str2.Trim();
}