Google Earth Runtime Error

Hi,

can anyone tell me why must I declare the variables

Code:

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(string earthVersion, string pluginVersion, string apiVersion)

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when using

Code:

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webBrowserGe.Url = new Uri("http://earthapi.googlepages.com/geToCs.html");

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or there will be a runtime error, whereas I do not need to declare it when I'm using a plugin, like,

Code:

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private const string PLUGIN_URL =
            @"http://earth-api-samples.googlecode.com/svn/trunk/demos/desktop-embedded/pluginhost.html";
        private void Form1_Load(object sender, EventArgs e)
        {
            webBrowser1.Navigate(PLUGIN_URL);
            webBrowser1.ObjectForScripting = this;
        }

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Is it because that the plugin has a declared variables in it? Thanks in advance