Not all code paths return a value in lambda expression of type 'System.Func' [duplicate]

Answer 1

It's easy. Don't forget to return the value:

Task<int> task1 = new Task<int>(()=> { return CountPixels(croppedBitmap, Color.FromArgb(255, 255, 255, 255)); });

Answer 2

Try (I've added the return keyword).

Task<int> task1 = new Task<int>(()=>{return CountPixels(croppedBitmap, Color.FromArgb(255, 255, 255, 255));})

Although CountPixels returns an int you're not returning that int in the task itself.

Answer 3

try removing the curly braces in your lambda statement:

Task<int> task1 = new Task<int>(()=> CountPixels(croppedBitmap, Color.FromArgb(255, 255, 255, 255)); );

There are different kinds of lamdas, for example this is an expression lambda (according to msdn):

(x, y) => x == y

It returns the result of the expression.

And this is the statement lambda:

(x, y) => { return x == y; }

So, when you use curly braces you are creating a statement lambda and there is no implicit returning, you have to explicitly use the return to return a value.