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，我在数据库中只得到连接失败消息框我发现正确，如何克服程序获取连接成功消息框

Answer 1

好吧，你正在填写ds数据集 - 但是你正在检查dt数据表中是否存在行......当然，它永远不会起作用！

如果您只需要一个DataTable - 只需单独使用和填充该数据表 - 无需DataSet的开销。另外，将SqlConnection和SqlCommand放入使用这样的块：

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");
    }
}

只是因为你回来dt.Rows中没有行并不一定意味着你的连接失败了.....可能只是没有符合你的搜索标准的行！连接工作得很好 - 但SQL命令只是没有返回任何行。

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。它只是意味着你的表是空的 - 它不包含任何记录。

使用ADO.NET和stored procedures会与您的操作略有不同。如果您需要检查连接是否失败，可能最好检查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看起来像这样：

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

     public string Name { get; set; }
}

存储过程看起来像这样：

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，您将获得聊天室并随心所欲地使用它。在这个例子中，我只是检查它是否存在：

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;
}

我希望这可以提供帮助。

如何使用ado.net调用存储过程

2 个答案: