我正在使用SQL Server 2008R2和VS 2010
我浏览时遇到此错误我尝试打开每个页面但弹出相同的错误。 请简单解释一下，简单地说一下我应该做什么我是新手。
[NullReferenceException: Object reference not set to an instance of an object.]
MyProject.login1.ImageButton3_Click（Object sender，ImageClickEventArgs e）位于C：\ Users \ prakash \ Desktop \ MyProject R2 \ MyProject R2 \ MyProject \ login1.aspx.cs：26 System.Web.UI.WebControls.ImageButton.OnClick（ImageClickEventArgs e）+115 System.Web.UI.WebControls.ImageButton.RaisePostBackEvent（String eventArgument）+124 System.Web.UI.WebControls.ImageButton.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent（String eventArgument）+10 System.Web.UI.Page.RaisePostBackEvent（IPostBackEventHandler sourceControl，String eventArgument）+13 System.Web.UI.Page.RaisePostBackEvent（NameValueCollection postData）+35 System.Web.UI.Page.ProcessRequestMain（Boolean includeStagesBeforeAsyncPoint，Boolean includeStagesAfterAsyncPoint）+1724
源代码
protected void ImageButton3_Click(object sender, ImageClickEventArgs e)
{
int flag = 0;
SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["shopingConnectionString1"].ConnectionString);
string s = "select * from login";
SqlCommand com = new SqlCommand(s, con);
con.Open();
if (con.State == ConnectionState.Open)
{
SqlDataReader dtr;
dtr = com.ExecuteReader();
while (dtr.Read())
{
if (dtr[0].ToString().Equals(TextBox1.Text) && dtr[1].ToString().Equals(TextBox2.Text))
{
Response.Cookies["uname"].Value = TextBox1.Text;
Response.Cookies["pwd"].Value = TextBox2.Text;
Response.Cookies["role"].Value = dtr[2].ToString();
FormsAuthentication.RedirectFromLoginPage(TextBox1.Text, false);
}
else
{
Label1.Text = "your credential are incorrect";
}