How to add or remove multiple Css Class names from CssClass property from code behind in ASP.Net

Please refer this code.

Below I am adding and removing CSS class for a Label control. Same way it can be done for Button using the CssClass property.

<style type="text/css">
    .Color
    {
        background-color: Yellow;
    }
    .FontSize
    {
        font-size: x-large;
    }
</style>
<div>
    <asp:Label ID="lblWelcome" Text="Welcome to AspForums.Net" runat="server" />
    <asp:Button ID="btnColor" runat="server" Text="Remove Font Size class" OnClick="RemoveClass" />
</div>

C#

protected void Page_Load(object sender, EventArgs e)
{
    this.lblWelcome.CssClass = "Color FontSize";
}

protected void RemoveClass(object sender, EventArgs e)
{
    this.lblWelcome.CssClass = "Color";
    this.btnColor.Text = "Class Removed";
}

Screenshots

Before Button Click

After Button Click