怎么限制文本框中输入的小数点的个数只能是一个

[ouguijiao]

在一个文本框中输入一串数字，可以包括小数点，但是要判断小数点只能输入一次

[shixiangzb007]

client code :

<form id="form1" runat="server">
<div>
<center>
<h1>you can only input one point into the textbox</h1>
<asp:TextBox ID="txt1" runat="server"></asp:TextBox>
<br />
<br />
<asp:Button ID="btn1" runat="server" Text="Validate" onclick="btn1_Click" />
<br />
<br />
<asp:Label ID="lbl1" runat="server"></asp:Label>
</center>
</div>
</form>

code behind:

protected void btn1_Click(object sender, EventArgs e)
{
string str = this.txt1.Text.ToString().Trim();
if (str.IndexOf(".") != -1)
{
if (str.IndexOf(".") != str.LastIndexOf("."))
{
this.lbl1.Text = "the first position is : " + str.IndexOf(".").ToString() +
"<br/>the last postion is : " + str.LastIndexOf(".").ToString();
}
}
}