在ADO.NET中处理“使用”语句

Question

I want to properly dispose the SqlConnection object whenever i come out of the method. So im using the "using" statement as shown below.

public int Hello()
{
   using(SqlConnection con=new SqlConnection(constring))
   {
      using(SqlCommand cmd=new SqlCommand(Query,con))
      {
       try
       {
          con.Open();
          return cmd.ExecuteNonQuery();
       }
       catch(Exception ex)
       {
          throw ex;
       }
       finally
       {
          con.Close()
       }
      }
   }
}

Now, what i want to know is, Will the above code

1. Dispose the Connection properly when an Exception is occured in ExecuteNonQuery.
2. Make sure we will not get any ConnectionPool issues
3. Make sure the data is returned properly
4. If an exception occurs in SqlConnection will it dispose the object?

Can anyone help me on this?

Answer 1

You don't need the try/catch if you're just going to throw it, just change your code to this:

public int Hello()
{
    using(SqlConnection con=new SqlConnection(constring))
    {
        using(SqlCommand cmd=new SqlCommand(Query,con))
        {
            con.Open();
            return cmd.ExecuteNonQuery();
        }
    }
}

and regardless of what happens, exception or not, the connection will get closed if it's open and disposed.

Answer 2

Dispose the Connection properly when an Exception is occured in ExecuteNonQuery. Yes

Make sure we will not get any ConnectionPool issues

i guess you mean connections would be properly relieved after executing query. if that is your question than You should not by using this approach.

Make sure the data is returned properly

using has nothing to do with returning data

If an exception occurs in SqlConnection will it dispose the object?

Yes

though you can rewrite your code as

using(SqlConnection con=new SqlConnection(constring))
   {
      using(SqlCommand cmd=new SqlCommand(Query,con))
      {
       try
       {
          con.Open();
          return cmd.ExecuteNonQuery();
       }
       catch(Exception ex)
       {
          throw;
       }       
      }
   }

Answer 3

You should not use the using statement for sqlconnection.

using(SqlConnection con=new SqlConnection(constring))

Better you use try,catch and finally block to close the connection. So even if exception occurs in try & catch the finally block will execute and close the connection if its open.

The reason behind this is, think of below situaion.

1. Create object of a class that handles all database operation eg DBUtility objDB = new DBUtility()

the above statement creates object of class and also initializes the sqlconnection variable from the constructor.

1. Now i am using the object objDB for executing multiple queries one by one. For this it should initialize the sqlconnection object only once and use it for its whole life (life obj objDB).

2. In your case the sqlconnection will be initialized as and when the method is called.

3. So simply init the connection once and open/close it for each of your operations. Your connection will automatically disposed by Garbage collector when objDB is disposed.