ClientScriptManager.RegisterStartupScript的使用

因为ClientScriptManager是一个密封类，因为平时编程中很少用到密封类，一时用常规的思维去使用，不成功，
的使用，后来我查了msdn,ClientScriptManager cs = Page.ClientScript; 但是密封类还和常规类一样的使用方法只是这个类没有构造函数，不能按照常规方法使用。

public void Page_Load(Object sender, EventArgs e)
{
// Define the name and type of the client scripts on the page.
String csname1 = "PopupScript";
String csname2 = "ButtonClickScript";
Type cstype = this.GetType();

// Get a ClientScriptManager reference from the Page class.
ClientScriptManager cs = Page.ClientScript;

// Check to see if the startup script is already registered.
if (!cs.IsStartupScriptRegistered(cstype, csname1))
{
String cstext1 = "alert('Hello World');";
cs.RegisterStartupScript(cstype, csname1, cstext1, true);
}

// Check to see if the client script is already registered.
if (!cs.IsClientScriptBlockRegistered(cstype, csname2))
{
StringBuilder cstext2 = new StringBuilder();
cstext2.Append("<script type="text/javascript"> function DoClick() {");
cstext2.Append("Form1.Message.value='Text from client script.'} </");
cstext2.Append("script>");
cs.RegisterClientScriptBlock(cstype, csname2, cstext2.ToString(), false);
}
}