c# - How to format a string as a number with leading zero

String format number leading zero
string-format-number-leading-zero.aspx

<%@ Page Language="C#" AutoEventWireup="true"%>
  
<!DOCTYPE html>  
<script runat="server"> 
    protected void Button1_Click(object sender, System.EventArgs e)  
    {
        //this line create a int variable.
        int number = 12345;

        Label1.Text = "formatted string..............";

        int length = number.ToString().Length + 1;
        string dValue = "D" + length.ToString();
        
        Label1.Text += "<br />Number: " + number;
        //format string using ToString method
        Label1.Text += "<br />String format number leading zero: " + number.ToString("D6");
        //format string using string.format method.
        Label1.Text += "<br />String format number leading zero: " + string.Format("{0:D6}",number);

        //dynamically determine number length and format string.
        Label1.Text += "<br /><br />Another dynamic option: " + number.ToString(dValue);
        //another technique to format string using padleft method.
        Label1.Text += "<br /><br />Another technique: " + number.ToString().PadLeft(length,'0');
    }  
</script>  
  
<html xmlns="http://www.w3.org/1999/xhtml">  
<head id="Head1" runat="server">  
    <title>c# example - string format number leading zero</title>  
</head>  
<body>  
    <form id="form1" runat="server">  
    <div>  
        <h2 style="color:MidnightBlue; font-style:italic;">  
            c# example - string format number leading zero
        </h2>  
        <hr width="550" align="left" color="Gainsboro" />  
        <br />
        <asp:Label   
            ID="Label1"   
            runat="server"  
            Font-Size="Large"  
            >  
        </asp:Label>  
        <br /><br />
        <asp:Button   
            ID="Button1"   
            runat="server"   
            Text="string format number leading zero"  
            OnClick="Button1_Click"
            Height="40"  
            Font-Bold="true"  
            />  
    </div>  
    </form>  
</body>  
</html>
More c# examples