How to change TextBox read only mode in asp.net

How to set, change TextBox read only mode (ReadOnly)
TextBox ReadOnly property help us to generate a textbox which are on read only mode. you cannot change, edit, write, delete or update text from read only textbox. this is a useful property when you want to make a textbox to disable editing for some user and dynamically enable textbox for writing to other user. this example demonstrate us the use of textbox ReadOnly property. here we uses a textbox and two button control. when you click a specified button then it change textbox for writable or read only mode. it also show how can we change textbox ReadOnly property value programmatically.
TextBoxReadOnly.aspx 

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

<!DOCTYPE html>

<script runat="server">
    protected void Button1_Click(object sender, System.EventArgs e)
    {
        TextBox1.ReadOnly = true;
    }
    protected void Button2_Click(object sender, System.EventArgs e)
    {
        TextBox1.ReadOnly = false;
    }
</script>

<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
    <title>How to set, change TextBox read only mode (ReadOnly)</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <h2 style="color:Green">TextBox Example: ReadOnly</h2>
        <asp:Label 
             ID="Label1" 
             runat="server"
             Text="Friend City"
             >
        </asp:Label>
        <asp:TextBox 
             ID="TextBox1" 
             runat="server"
             >
        </asp:TextBox>
        <br /><br />
        <asp:Button 
             ID="Button1" 
             runat="server" 
             ForeColor="Crimson"
             Text="Set ReadOnly Mode"
             OnClick="Button1_Click"
             Font-Bold="true"
             />
        <asp:Button 
             ID="Button2" 
             runat="server" 
             Font-Bold="true"
             ForeColor="Crimson"
             Text="Clear ReadOnly Mode"
             OnClick="Button2_Click"
             />
    </div>
    </form>
</body>
</html>
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