使用存儲過程使用C＃從sql數據庫檢索數據

Question

每當我嘗試從我的數據庫中檢索數據時，我總是收到空值。我使用的代碼如下：

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

你需要調用Read才能訪問數據，你的代碼應該是

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(); 

Answer 2

在您閱讀從DataReader的列值必須調用從數據讀取器Read()方法。

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

你還可以嘗試：

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

Answer 3

SqlDataReader myReader = myCommand.ExecuteReader(CommandBehavior.CloseConnection); 
while(myReader.Read()) 
{ 
Console.WriteLine(myReader.GetString(0)); 
} 
myReader.Close(); 

//隱式地關閉連接因爲CommandBehavior.CloseConnection被指定。

文檔： http://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlcommand.executereader(v=vs.71).aspx

Answer 4

你缺少你的讀者Read()通話。我還建議你將IDisposable對象包含在using聲明中，如下所示。

從SqlDataReader檢索您的值時，您似乎也在使用列名稱和序數位置的奇怪組合。

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

      SqlParameter custId = cmd.Parameters.AddWithValue("@CustomerId", 10); 

      using (SqlDataReader dr = cmd.ExecuteReader()) 
      { 
       if (dr.Read()) 
       { 
        Label1.Text = dr["FirstName"].ToString(); 
        Label2.Text = dr["LastName"].ToString(); 
        Label3.Text = dr[3].ToString(); 
        Label4.Text = dr["Email"].ToString(); 
       } 
      } 
     } 
    } 
}