连接sql server的try{}catch怎么写

Question

就是说我连接数据库有可能会出现登录失败的情况，应该怎么写try{???

Answer 1

Public Function openConn() As String
        '
        Try
            ConnSQLStr = "Data Source=" & strDataSource & _
                         ";User ID=" & strUserID & _
                         ";Password=" & strPassword            myORACLEConnection.ConnectionString = ConnSQLStr
            If myORACLEConnection.State = ConnectionState.Open Then
                myORACLEConnection.Close()
            End If
            myORACLEConnection.Open()            Return "数据库连接成功，当前连接数据库：【" & strDataSource & "】"
        Catch ex As Exception
            Return "连接【" & strDataSource & "】数据库失败。"
        End Try
    End Function

Answer 2

using (OdbcConnection connection = new OdbcConnection(connectionString))
{
       try
       {
              dadapter.SelectCommand.Connection = connection;
               
              OdbcCommandBuilder builder = new OdbcCommandBuilder( dadapter );               connection.Open();
              dadapter.Update(dset, "payunit");
         }
         catch ( Exception ex )
         {
                  //  exception handling code.    
         }
         finally
         {
                 connection.Close();
         }
   }      //  connection object is disposed.    

Answer 3

using (OdbcConnection connection = new OdbcConnection(connectionString))
{
       try
       {
              //...
         }
         catch ( SqlException ex )
         {
                  //  ...
                  transaction.commit();
         }
         finally
         {
                 transaction.rollBack();
                 connection.Close();
         }
   }      //  connection object is disposed.    

Answer 4

Try 
/*定义connection，略
*/
   If Connection.State = ConnectionState.Open Then 
      Connection.Close() 
   End If 
   Connection.Open() 
Catch ex As Exception 
   Return "Connect failed" 
End Try 

Answer 5

C# Code
using (OdbcConnection con= new OdbcConnection(connectionString))
{
        try
        {
              dadapter.SelectCommand.Connection = con;      
              OdbcCommandBuilder builder = new OdbcCommandBuilder(dadapter); 
              con.Open();
              dadapter.Update(dset, "payunit");
         }
         catch (Exception ex){ }  
         finally{con.Close();}
   }