How to use AddJavaScriptMessageHandler of webview to send message from JavaScript?

c#

try
{
    this.control = (T.WebView)this.NativeView;
    if (this.control != null)
    {
        bool bok = this.control.AddJavaScriptMessageHandler("test", new T.JavaScriptMessageHandler(this.OnJavaScriptCall));
        System.Diagnostics.Debug.WriteLine(bok);

    }
    
}
catch
{
}

JavaScript:

<script type="text/javascript">
    alert(test);
</script>

test is null on Html…. who can help me?