如何使用 ado.net 调用存储过程

Question

private void button1_Click(object sender, EventArgs e)
{
    try
    {
        SqlConnection conn = new SqlConnection();
        conn.ConnectionString = "Data Source=*******;Initial Catalog=ChatApp;User ID=Chatapplication;Password=****";
        conn.Open();
        SqlCommand cmd = new SqlCommand();
        string chatroomidno = textBox1.Text;
        string chatroomname = textBox2.Text;
        //cmd.CommandText = "Select ChatRoomID=@ChatRoomID,ChatRoomName=@ChatRoomName from tblChatRoom";
        //cmd.Connection = conn;
        SqlDataAdapter adapt = new SqlDataAdapter("Chatroomapp",conn);
        adapt.SelectCommand.CommandType = CommandType.StoredProcedure;
        DataSet ds=new DataSet();
        DataTable dt = new DataTable();
        adapt.SelectCommand.Parameters.Add(new SqlParameter("@ChatRoomID", SqlDbType.VarChar, 100));
        adapt.SelectCommand.Parameters["@ChatRoomID"].Value = chatroomidno;
        adapt.SelectCommand.Parameters.Add(new SqlParameter("@ChatRoomName", SqlDbType.VarChar, 50));
        adapt.SelectCommand.Parameters["@ChatRoomName"].Value = chatroomname;
        adapt.Fill(ds, "tblChatRoom");
        if (dt.Rows.Count > 0)
        {
            MessageBox.Show("Connection Succedded");
        }
        else
        {
            MessageBox.Show("Connection Fails");
        }
    }
    catch (Exception ex)
    {
        MessageBox.Show("Error", ex.Message);
    }
}

在编译程序时，我在数据库中只收到连接失败消息框。我发现正确，如何克服程序以获取连接成功消息框。

Answer 1

好吧，您正在填充 ds 数据集 - 但随后您正在检查 dt 数据表中是否存在行...当然，这永远不会起作用！

如果您只需要一个 DataTable - 只需单独使用和填写该数据表 - 不需要 DataSet 的开销。另外，将您的 SqlConnection 和 SqlCommand 放入 using 块中，如下所示：

using (SqlConnection conn = new SqlConnection("Data Source=*******;Initial Catalog=ChatApp;User ID=Chatapplication;Password=****"))
using (SqlCommand cmd = new SqlCommand("Chatroomapp", conn))
{
    string chatroomidno = textBox1.Text;
    string chatroomname = textBox2.Text;

    SqlDataAdapter adapt = new SqlDataAdapter(cmd);
    adapt.SelectCommand.CommandType = CommandType.StoredProcedure;
    adapt.SelectCommand.Parameters.Add(new SqlParameter("@ChatRoomID", SqlDbType.VarChar, 100));
    adapt.SelectCommand.Parameters["@ChatRoomID"].Value = chatroomidno;
    adapt.SelectCommand.Parameters.Add(new SqlParameter("@ChatRoomName", SqlDbType.VarChar, 50));
    adapt.SelectCommand.Parameters["@ChatRoomName"].Value = chatroomname;

    // fill the data table - no need to explicitly call `conn.Open()` - 
    // the SqlDataAdapter automatically does this (and closes the connection, too)
    DataTable dt = new DataTable();
    adapt.Fill(dt);

    if (dt.Rows.Count > 0)
    {
       MessageBox.Show("Connection Succedded");
    }
    else
    {
       MessageBox.Show("Connection Fails");
    }
}

仅仅因为您在dt.Rows 中没有返回任何行并不一定意味着您的连接失败......可能只是没有符合您的搜索条件的行！连接工作得很好——但 SQL 命令没有返回任何行。

Answer 2

连接失败意味着您的程序和数据库之间出现了问题。没有返回记录并不意味着连接失败。这只是意味着您的表是空的 - 它不包含任何记录。

使用ADO.NET 和stored procedures 会与您所做的有所不同。如果您需要检查连接是否失败，最好检查catch 部分中返回的异常类型。

以下是我将如何做到的。我会创建一个单独的方法来处理我的调用，然后在你的button1_Click 中我会调用这个方法：

public async Task<ChatRoom> GetAsync(string chatRoomId, string chatRoomName)
{
     try
     {
          string connectionString = ConfigurationManager.ConnectionStrings["Db"].ConnectionString;

          using (SqlConnection sqlConnection = new SqlConnection(connectionString))
          {
               await sqlConnection.OpenAsync();

               using (SqlCommand sqlCommand = new SqlCommand("ChatRooms_Get", sqlConnection))
               {
                    sqlCommand.CommandType = CommandType.StoredProcedure;
                    sqlCommand.Parameters.Add(new SqlParameter("@ChatRoomID", chatRoomId));
                    sqlCommand.Parameters.Add(new SqlParameter("@ChatRoomName", chatRoomName));

                    using (SqlDataReader sqlDataReader = await sqlCommand.ExecuteReaderAsync())
                    {
                         ChatRoom chatRoom = null;

                         if (await sqlDataReader.ReadAsync())
                         {
                              chatRoom = new ChatRoom();
                              chatRoom.Id = sqlDataReader.GetFieldValue<string>(0);
                              chatRoom.Name = sqlDataReader.GetFieldValue<string>(1);

                              chatRooms.Add(chatRoom);
                         }

                         return chatRoom;
                    }
               }
          }
     }
     catch (Exception exception)
     {
          // Try checking if the connection failed here

          throw exception;
     }
}

我的聊天室domain model 可能看起来像这样：

public class ChatRoom
{
     public string Id { get; set; }

     public string Name { get; set; }
}

存储过程应该是这样的：

CREATE PROCEDURE [dbo].[ChatRooms_Get]
(
     @ChatRoomID VARCHAR(100),
     @ChatRoomName VARCHAR(50)
)
AS
BEGIN
     SET NOCOUNT ON;

     SELECT
          ChatRoomID,
          ChatRoomName
     FROM
          tblChatRoom
     WHERE
          ChatRoomID = @ChatRoomID
          AND ChatRoomName = @ChatRoomName;
END

GO

然后在调用方法中，您将获得聊天室并使用它做任何您需要做的事情。对于这个例子，我只是检查了它是否存在：

try
{
     ChatRoom chatRoom = await chatRoomRepository.GetAsync(chatRoomId, chatRoomName);
     if (chatRoom != null)
     {
          MessageBox.Show("Record found");
     }
     else
     {
          MessageBox.Show("No record found");
     }
}
catch (Exception exception)
{
     throw exception;
}

我希望这会有所帮助。