[Proposal]: Null conditional assignment

[RikkiGibson]

• Speclet: https://github.com/dotnet/csharplang/blob/main/proposals/null-conditional-assignment.md
• Discussion: Null-conditional assignment #8676

Summary

Permits assignment to occur conditionally within a a?.b or a?[b] expression.

using System;

class C
{
    public object obj;
}

void M(C? c)
{
    c?.obj = new object();
}

using System;

class C
{
    public event Action E;
}

void M(C? c)
{
    c?.E += () => { Console.WriteLine("handled event E"); };
}

void M(object[]? arr)
{
    arr?[42] = new object();
}

Design meetings

• https://github.com/dotnet/csharplang/blob/main/meetings/2022/LDM-2022-04-27.md#null-conditional-assignment
• https://github.com/dotnet/csharplang/blob/main/meetings/2022/LDM-2022-08-31.md#null-conditional-assignment
• https://github.com/dotnet/csharplang/blob/main/meetings/2022/LDM-2022-10-26.md#null-conditional-assignment
• https://github.com/dotnet/csharplang/blob/main/meetings/2024/LDM-2024-10-28.md#increment-and-decrement-operators-in-null-conditional-access