Lambda closures in C#

In C#, a lambda expression can capture variables from its enclosing scope, creating what is known as a closure. This allows the lambda to access and modify those variables even after the scope in which they were defined has ended.

var f = fn();
// 0
Console.WriteLine(f());
// 1
Console.WriteLine(f());

static Func<int> fn()
{
    int i =0;
    return ()=> i++;
}

static lambdas

In C# 9.0 and later, can be declared a lambda expression as static, which means it cannot capture any variables from its enclosing scope. This can improve performance and reduce memory allocation since the lambda does not need to create a closure.

static Func<int> fn()
{
    int i =0;
    return static () => 
    //i++; // Compilation Error: Cannot modify 'i' because it is not in scope
    0
    ;
}