HTML5有新标签文章，部分和旁边。(HTML5 has new tags article, section and aside. When should I use div tag?)

 更改您的代码如下（我假设URLInput是主窗体上的控件）： 
 
private void HomePage_Click(object sender, EventArgs e)
{
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(URLInput.Text);
    HttpWebResponse response = (HttpWebResponse)request.GetResponse();
    StreamReader sr = new StreamReader(response.GetResponseStream());
    richTextBox1.Text = sr.ReadToEnd();
}

private void ChangeHomeToolStripMenuItem_Click(object sender, EventArgs e)
//this is menu item to call 
{
    using(Home h = new Home())
    {
        h.ShowDialog();
        var homePageUrl = h.getHomePage();
        if (string.IsNullOrEmpty(homePageUrl))
            return;
        URLInput.Text = homePageUrl;
    }
}

Change your code as follows (I assume that URLInput is a control on the main form):
 
private void HomePage_Click(object sender, EventArgs e)
{
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(URLInput.Text);
    HttpWebResponse response = (HttpWebResponse)request.GetResponse();
    StreamReader sr = new StreamReader(response.GetResponseStream());
    richTextBox1.Text = sr.ReadToEnd();
}

private void ChangeHomeToolStripMenuItem_Click(object sender, EventArgs e)
//this is menu item to call 
{
    using(Home h = new Home())
    {
        h.ShowDialog();
        var homePageUrl = h.getHomePage();
        if (string.IsNullOrEmpty(homePageUrl))
            return;
        URLInput.Text = homePageUrl;
    }
}