c# - 使用C#和存储过程从sql数据库中检索数据

Question

每当我尝试从我的数据库中检索数据时，我总是得到 null。我使用的代码如下:

protected void Button2_Click(object sender, EventArgs e)
 {
    SqlConnection myConnection = new SqlConnection(GetConnectionString());
    SqlCommand cmd = new SqlCommand("spSelectCustomer", myConnection);
    cmd.CommandType = CommandType.StoredProcedure;
    myConnection.Open();

    SqlParameter custId = cmd.Parameters.Add("@CustomerId", SqlDbType.Int);
    custId.Direction = ParameterDirection.Input;
    custId.Value = 10;

    SqlDataReader dr = cmd.ExecuteReader(CommandBehavior.CloseConnection);

    Label1.Text = dr["FirstName"].ToString();
    Label2.Text = dr["LastName"].ToString();
    Label3.Text = dr[3].ToString();
    Label4.Text = dr["Email"].ToString();
}
private static string GetConnectionString()
{
    return ConfigurationManager.ConnectionStrings["Lab3ConnectionString"].ConnectionString;
}

Answer 1

你需要先调用Read才能访问数据，你的代码应该是

While (dr.Read())
{

    Label1.Text = dr["FirstName"].ToString();
    Label2.Text = dr["LastName"].ToString();
    Label3.Text = dr[3].ToString();
    Label4.Text = dr["Email"].ToString();
}

//close DataReader
dr.Close();