c# - How to replace a substring of a string

String Replace() Method

in .net framework we can replace a string or a substring from a specified string with another string. String.Replace(String, String) method allow us to replace a string with another string.

this method returns a new string in which all occurrences of a specified string in the current instance are replaced with another specified string. Replace method require two parameters. both parameters type is System.String. first parameter's name is oldValue that the string to be replaced. and second parameter's name is newValue that the string replace all occurrences of old value.

if the method does not find oldValue in the current instance then it returns the current instance unchanged. otherwise it replace the string with specified string and return a new string.

this method performs an ordinal (case sensitive and culture insensitive) search to find oldValue.

String.Replace(Char, Char) method returns a new string in which all occurrences of a specified Unicode character in this instance are replaced with another specified Unicode character.

the following asp.net c# example code demonstrate us how can we perform string replace in .net framework.

Replace.aspx


<%@ Page Language="C#" %>
<!DOCTYPE html>

<script runat="server">
    protected void page_Load(object sender, System.EventArgs e) {
        if(!this.IsPostBack)
        {
            TextBox1.Text = "This is a sample string.";
        }
    }
    protected void Button1_Click(object sender, System.EventArgs e) {
        string myString = TextBox1.Text.ToString();
        string replaceString = myString.Replace("sample","test");

        Label1.Text = "String replaced successfully [sample with test]!";
        TextBox1.Text = replaceString;
    }
</script>

<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
    <title>How to replace a specified substring with another string in asp.net</title>
</head> 
<body>
    <form id="form1" runat="server">
    <div>
        <h2 style="color:Maroon">asp.net string example: Replace()</h2>
        <asp:Label 
             ID="Label1" 
             runat="server" 
             Font-Size="Large"
             ForeColor="Red"
             Font-Bold="true"
             Font-Italic="true"
             >
        </asp:Label>
        <br /><br />
        <asp:Label 
             ID="Label2" 
             runat="server" 
             Text="Test String"
             ForeColor="DarkSlateBlue"
             >
        </asp:Label>
        <asp:TextBox 
             ID="TextBox1" 
             runat="server" 
             BackColor="DarkSlateBlue" 
             ForeColor="AliceBlue"
             >
        </asp:TextBox>
        <br /><br />
        <asp:Button 
             ID="Button1" 
             runat="server" 
             OnClick="Button1_Click"
             Font-Bold="true"
             Text="Replace sample With test"
             ForeColor="DarkSlateBlue"
             />   
    </div>
    </form>
</body>
</html>

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