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C#: with

Handbook C# · Practical Guide

Creates a modified copy of a record, struct, or anonymous object. Reference-valued members are copied shallowly.

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
var original = new Item("ore", 1);
var copy = original with { Count = 3 };
System.Console.WriteLine($"{original.Count}:{copy.Count}");
record Item(string Name, int Count);

Result:

1:3

Syntax

var changed = original with { Member = value };

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)
    {
        Person first = new("Archer", 2);
        Person next = first with { Level = 3 };
        Console.WriteLine($"{first.Level}:{next.Level}");
    }
}
public record Person(string Name, int Level);

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)
    {
        var first = new { Name = "Ore", Count = 5 };
        var next = first with { Count = 8 };
        Console.WriteLine($"{first.Count}:{next.Count}");
    }
}

Official source: Microsoft Learn.