在ExecuteReader()之前

试试这个

sqlconnection.Open();

Before ExecuteReader()

try this

sqlconnection.Open();

SqlConnection con =新的SqlConnection("Server =(local)\\ SQLEXPRESS; Initial Catalog = Northwind; Integrated Security = SSPI");

SqlCommand cmd =新的SqlCommand();

cmd.CommandText ="SELECT EmployeeID，FirstName +``''+ LastName作为来自员工的FullName";

cmd.Connection = con;

SqlConnection con = new SqlConnection("Server=(local)\\SQLEXPRESS;Initial Catalog=Northwind;Integrated Security=SSPI");

SqlCommand cmd = new SqlCommand();

cmd.CommandText = "SELECT EmployeeID, FirstName + '' '' + LastName as FullName FROM Employees";

cmd.Connection = con;

if (con.State == System.Data.ConnectionState.Open)
        {
            con.Close();
        }

con.Open();

SqlDataReader reader = cmd.ExecuteReader();

while(reader.Read()){

}

reader.Close();
con.Close();


或

还请检查下面的链接
http://forums.asp.net/post/4623355.aspx [

con.Open();

SqlDataReader reader = cmd.ExecuteReader();

while (reader.Read()) {

}

reader.Close();
con.Close();


or

also check below link
http://forums.asp.net/post/4623355.aspx[^]