Cannot assign void to an implicitly-typed local variable with var and foreach

c# foreach lambda var
tonni picture tonni · Apr 2, 2014 · Viewed 48.4k times · Source

I'm trying to list all buttons name from my form to list with code 

var v = new List<Form1>() { this }.ForEach(x => { x.GetType().Name.Contains(typeof(Button).Name); });

and always get error

Cannot assign void to an implicitly-typed local variable

How to bypass that?

Answer

Habib picture Habib · Apr 2, 2014

Foreach returns void that is why you are getting the error. Your statement on the right hand side of assignment is not returning anything. You can do the same in two statements like:

var v = new List<Form1>() { this };
v.ForEach(x => { x.GetType().Name.Contains(typeof(Button).Name); });

In your current code you are creating a new List<Form1> and then iterating over each item in the list, but you are not returning anything.

As Jon Skeet has pointed out in the comment, it will not have any effect on the list. I guess you are trying to get all the button from your list of forms you can do:

var allButtons = v.SelectMany(r => r.Controls.OfType<Button>()).ToList();

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