c# - How to perform string replace by ignoring case

String replace ignore case
string-replace-ignore-case.aspx

<%@ Page Language="C#" AutoEventWireup="true"%>

<!DOCTYPE html>  
<script runat="server"> 
    protected void Button1_Click(object sender, System.EventArgs e)  
    {
        //this section create a string variable.
        string stringValue = "red green Red yellow darkRed";

        Label1.Text = "string..................<br />";
        Label1.Text += stringValue.ToString();

        //this section replace substring with substring in string ignore case.
        string replacedString = Regex.Replace(stringValue, "red", "blue", RegexOptions.IgnoreCase);

        Label1.Text += "<br /><br />modified string......................";
        Label1.Text += "<br />" + replacedString.ToString();
    }  
</script>  
  
<html xmlns="http://www.w3.org/1999/xhtml">  
<head id="Head1" runat="server">  
    <title>c# example - string replace ignore case</title>  
</head>  
<body>  
    <form id="form1" runat="server">  
    <div>  
        <h2 style="color:MidnightBlue; font-style:italic;">  
            c# example - string replace ignore case
        </h2>  
        <hr width="550" align="left" color="Gainsboro" />  
        <asp:Label   
            ID="Label1"   
            runat="server"  
            Font-Size="Large"
            Font-Bold="true"
            >  
        </asp:Label>  
        <br /><br />
        <asp:Button   
            ID="Button1"   
            runat="server"   
            Text="string replace ignore case"  
            OnClick="Button1_Click"
            Height="40"  
            Font-Bold="true"  
            />  
    </div>  
    </form>  
</body>  
</html>
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