ASP.NET

public MyClass
{
  public MyClass(){...}
  GetSomeDataById(string id)
  {
    try
       {
          // Open connection and all that good stuff
          ...
       }
     Catch
       { /* Catch*/ }
     finallay
       {
         /* close connection */ 
       }
  }
}
--------------------------------------------------------------
// in .aspx file
 MyClass myClass = new MyClass("whatever");
   string someData = myClass.GetSomeDataGyId("10");
   if(String.IsNullOrEmply(someData)
   {
      // Some code
   }

public MyClass
{
  public MyClass(){...}
  GetSomeDataById(string id)
  {
       // Open connection and all that good stuff 
       ....
       // close connection
  }
}

-------------------------------------------------
//in aspx file
try
{
   MyClass myClass = new MyClass("whatever");
   string someData = myClass.GetSomeDataGyId("10");
   if(String.IsNullOrEmply(someData)
   {
      // Some code
   }
}
catch Exception(e)
{
    // Call some function to display this message
}