Handling User Defined SQL Exceptions in C# 7

Written by Khalid Abuhakmeh
2
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Let’s say you are developing a new Infinity War SQL stored procedure. Thanos, your boss, has explicity told you to add validation to a stored procedure and warn developers of their impending doom. To halt the execution of the stored procedure, you may decide to THROW an exception like so:

;THROW 50001,'I know what it''s like to lose; to feel so desperately that you''re right, yet fail all the same.',1;

Note that the line of SQL throws a 50001 which denotes the error as being user defined. Now, to deal with those developers.

In C#, we can use pattern matching to catch the SqlException and convert it into a helpful message.

try {
    // Execute SQL Command
} catch (SqlException e) 
  when (e.Number == 50001) {
      return new ThanosQuoteResult(e.Message);
  }

Note that you want to look at the Number property on a SqlException and not the ErrorCode.

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