我的选择命令不起作用

Question

我正在使用Visual Studio 2010，并且添加了一个新项目作为report.mdf作为我的项目数据库;我创建了一个表Table1，并且我手动添加了一条记录到Table1;但是当我试图选择数据，我不能做到这一点，得到这个错误：

invalid attempt to read when no data is present

这是我的代码：

SqlCommand objcomand = new SqlCommand(); 

SqlConnection con = new SqlConnection(); 
con.ConnectionString=@"Data Source=.\SQLEXPRESS;AttachDbFilename=C:\Users\EHSAN\My Documents\Visual Studio 2010\Projects\report\report\App_Data\report.mdf;Integrated Security=True;User Instance=True"; 

objcomand.Connection = con; 
objcomand.CommandText = "select * from Table1"; 

con.Open(); 

SqlDataReader reader1 = objcomand.ExecuteReader(); 
string i = reader1.GetValue(1).ToString(); 

con.Close(); 

Answer 1

你必须在DataReader推进到数据的下一个块SqlDataReader.Read：

string i = null; 
// use using for everything that implements IDisposable like a Connection or a DataReader 
using(var reader1 = objcomand.ExecuteReader()) 
{ 
    // a loop since your query can return multiple records 
    while(reader1.Read()) 
    { 
     // if the field actually is the first you have to use GetString(0) 
     i = reader1.GetString(1); 
    } 
}