Update all objects in a collection using LINQ

While you can use a ForEach extension method, if you want to use just the framework you can do

collection.Select(c => {c.PropertyToSet = value; return c;}).ToList();

The ToList is needed in order to evaluate the select immediately due to lazy evaluation.

collection.ToList().ForEach(c => c.PropertyToSet = value);

I am doing this

Collection.All(c => { c.needsChange = value; return true; });