Multiple catch blocks in C Sharp (C#) - Step-by-Step Execution

Concept Flow - Multiple catch blocks

Try block starts

↓

Code runs

↓

Exception thrown?

No→Try block ends normally

Yes↓

Check first catch block type

↓

Matches

↓

Run catch

↓

Catch block ends

↓

Continue after try-catch

The program tries code in the try block. If an error happens, it checks each catch block in order to find one matching the error type and runs it.

Execution Sample

C Sharp (C#)

try {
  int x = int.Parse("abc");
} catch (FormatException) {
  Console.WriteLine("Format error");
} catch (Exception) {
  Console.WriteLine("General error");
}

This code tries to convert a string to a number. If it fails with a format error, it prints "Format error". For other errors, it prints "General error".

Execution Table

Step	Action	Exception Thrown?	Catch Block Checked	Catch Block Matches?	Output
1	Enter try block, execute int.Parse("abc")	Yes: FormatException	FormatException catch	Yes
2	Run FormatException catch block	No			Format error
3	Exit try-catch, continue program	No

💡 Exception FormatException caught by first catch block, program continues after try-catch.

Variable Tracker

Variable	Start	After Step 1	After Step 2	Final
x	undefined	Exception thrown, x not assigned	Not assigned	Not assigned

Key Moments - 2 Insights

Why does the first catch block run instead of the second?

Because the exception thrown is FormatException, which matches the first catch block type exactly (see execution_table step 1). The second catch block is for general Exception and is skipped.

What happens if no catch block matches the exception?

The exception is unhandled and the program crashes or moves to a higher-level handler. In this example, all exceptions are caught by the two catch blocks, so this does not happen.

Visual Quiz - 3 Questions

Look at the execution table, which catch block handles the exception?

A The first catch block for FormatException

B The second catch block for Exception

C No catch block handles it

D Both catch blocks handle it

💡 Hint

See execution_table row 1 and 2 where FormatException catch block matches and runs.

At which step does the program output "Format error"?

A Step 1

B Step 2

C Step 3

D No output is produced

💡 Hint

Check execution_table row 2 where the catch block runs and prints output.

If the thrown exception was NullReferenceException, which catch block would run?

A FormatException catch block

B Exception catch block

C No catch block

D Both catch blocks

💡 Hint

NullReferenceException is a general Exception but not FormatException, so second catch block matches.

Concept Snapshot

try {
  // code that may throw
} catch (SpecificException) {
  // handle specific error
} catch (Exception) {
  // handle other errors
}

- Multiple catch blocks checked in order
- First matching catch runs
- Program continues after catch

Full Transcript

This example shows how multiple catch blocks work in C#. The program tries to run code inside the try block. If an error happens, it looks at each catch block in order. If the error type matches the catch block type, that block runs. In the example, parsing "abc" to int throws a FormatException. The first catch block matches this type and runs, printing "Format error". The second catch block is skipped. After the catch block finishes, the program continues normally. If no catch block matches, the program would crash or look for a higher-level handler. This shows how you can handle different errors differently by using multiple catch blocks.