EN CSharp Keyword catch

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C#: catch

Handbook C# · Practical Guide

Handles an exception of the appropriate type; when can filter exceptions.

Simple example (Example.cs)

Save this example separately as Example.cs. Run it independently of the other examples on this page.

Example.cs:

// PROJECT-EXAMPLE
try { int.Parse("not a number"); }
catch (System.FormatException) { System.Console.WriteLine("Invalid"); }

Result:

Invalid

Syntax

catch (Exception error) when (condition) { ... }

Example 1: simple form

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.IO;
using System.Runtime.InteropServices;
using System.Runtime.CompilerServices;

public static class Program
{
    public static async Task Main(string[] args)
    {
        try { int number = int.Parse("invalid"); Console.WriteLine(number); }
        catch (FormatException error) { Console.WriteLine(error.Message); }
        finally { Console.WriteLine("Finished"); }
    }
}

Example 2: another practical form

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.IO;
using System.Runtime.InteropServices;
using System.Runtime.CompilerServices;

public static class Program
{
    public static async Task Main(string[] args)
    {
        try { Validation.Positive(-1); }
        catch (ArgumentOutOfRangeException error) when (error.ParamName == "value") { Console.WriteLine("Negative value"); }
        finally { Console.WriteLine("Cleanup"); }
    }
}
public static class Validation { public static void Positive(int value) { if (value < 0) throw new ArgumentOutOfRangeException(nameof(value)); } }

Official source: Microsoft Learn.