Component level variable : Basics « Custom Controls « ASP.NET Tutorial

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<%@Import Namespace="System.Drawing" %>
<%@Register TagPrefix="CodingStrategies" TagName="Color" Src="Control.ascx" %>
<script language="C#" runat="server">
protected void SetColor(object o, EventArgs e) {
    Color color = Color.FromName(theTextbox.Text);
    colorControl.Color = color;
}
</script>
<form runat="server">
Name your favorite color
<asp:textbox runat="server" id="theTextbox" OnTextChanged="SetColor" Value="Black"/><br />
Your favorite color is: <CodingStrategies:Color runat="server" id="colorControl" /><br />
<asp:button type="submit" runat="server" Text="Go" />
</form>

File: Control.ascx

<%@Import namespace="System.Drawing" %>
<script runat="server" language="C#">
protected Color favoriteColor = Color.Black;
protected void Page_Load(Object o, EventArgs e) {
    theLabel.Text = favoriteColor.Name;   
}
public Color Color {
    set {
        favoriteColor = value;
        theLabel.Text = favoriteColor.Name;
        theLabel.ForeColor = favoriteColor;
    }
}
</script>
<h2><asp:label id="theLabel" runat="server"/></h2>