using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
publicpartialclass_Default : System.Web.UI.Page
{
protectedvoid Page_PreInit(object sender, EventArgs e)
{
Page.MasterPageFile = "~/MasterPage.master";
}
protectedvoid Page_Load(object sender, EventArgs e)
{
MasterPage mp = (MasterPage)Page.Master;
mpLabel.Text = Master.myValue;
}
protectedvoid Button1_Click(object sender, EventArgs e)
{
Label1.Text = TextBox1.Text;
TextBox1.Text = "";
}
}

Cannot convert type 'System.Web.UI.Page' to MasterPage'