Catch REFERENCE constraint exception from SQL in C#

Question

What will be proper way to catch exception which throw SQL server when I deleting data with Reference constraint from C# code.
I want to show my users message like:
"I can't delete the data because is used"
, rather than of showing message like this:

The DELETE statement conflicted with the REFERENCE constraint ... The conflict ccurred*in database "rampa", table "dbo.doc", column 'kartica_id'.

Answer 1

I don't know about SQL server but most DBMSs clients throw an exception of a specific type (SQLCommandException for instance) which contains an error code

You should be able to catch the exception with a try catch block and check the error code property on the exception in the catch block

try
{
  // Perform your delete
}
catch (SQLCommandException e)
{
  if (e.ErrorCode == 5678)
  {
    // Friendly message handling
  }
}

Answer 2

You can access the ConstraintException and map its fields however you want to your own preferred error output.

using System.Data;

try
{
  // code that violates constraint
}
catch (ConstraintException exc)
{
  // build output message you wish using exc.Message and other fields,
  // return cleanly or rethrow as your own exception
}

Answer 3

Use this:

try
{
   //Execute delete statement
}
catch (SqlException sqlEx)
{
   //Handle exception
}
finally
{
   //Close connection
}

All sql errors are thrown as SqlException and there are no specific errors. To find out what was error exactly, there is property SqlException.Number which is the same as SQL Error Code. You can find list of codes here.