Introduction
"A group of characters known as string", Like "Hello World!". If you want to change in it, use StringBuilder class, which is a mutable string class. Mutable means, if you want create an object with some character value, also want to change in it further , that is possible with same object. So here we take StringBuilder class for appending string.<form id="form1" runat="server">
<asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Button"
Width="68px" BackColor="#FFFF66" />
<div style="width: 88px">
<asp:Label ID="Label1" runat="server" Text="Label" BackColor="#FFCC66"
BorderColor="#CC0000"></asp:Label>
</div>
</form>
Business Logic Code
protected void Button1_Click(object sender, EventArgs e){
StringBuilder stringd = new System.Text.StringBuilder();
stringd.AppendLine("those are string.");
stringd.AppendLine(" [ ");
stringd.Append('H');
stringd.AppendLine(" ] ");
stringd.AppendLine("those are another string");
Label1.Text = stringd.ToString();
}