How to create a dynamic lambda to use it?

Question

I've learned to manipulate Dynamic lambda expressions with the Expression class. However, the lambda expression used in a ForEach method (LINQ) seems a little different since it's an assign.

For exemple, doing this :

myList.ForEach(x => x.Status = "OK") ;

will update the Status property of each object in the myList list.

How to accomplish it using Expression object? I didn't find any method in Expression to set a property... Is it used only for retrieving properties values ?

What version of .NET are you using? V4 has it, while earlier versions don't. — Gabe
– Gabe, Commented Nov 25, 2011 at 16:36

Jon Skeet · Accepted Answer · 2011-11-25 16:26:15Z

6

Assignment does exist in expression trees (see Expression.Assign) as of .NET 4 (where it's used to support dynamic), but it's not supported by the C# compiler, which still only supports genuine "expressions" for lambda expression conversions to expression trees.

answered Nov 25, 2011 at 16:26

Jon Skeet

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Comments

Dan Tao · Accepted Answer · 2011-11-25 16:46:15Z

1

I'm pretty sure Linq Expressions does not support assigning. I think you'd need to write a method with assignment in it and put that in the expression.

Update: Looks like assignment is supported as of .NET 4. See Jon Skeet's answer.

edited Nov 25, 2011 at 16:46

answered Nov 25, 2011 at 16:27

Dan Tao

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Iesvs · Accepted Answer · 2011-11-25 16:26:57Z

0

You can do :

myList.ForEach(x =>
{
    x.Status = "OK";
});

or

Action<YourType> oSetter = x =>
{
    x.Status = "OK";
});
myList.ForEach(oSetter);

answered Nov 25, 2011 at 16:26

Iesvs

11

2 Comments

Gabe Over a year ago

You just said the same thing as the OP.

Iesvs Over a year ago

Oh sorry I misunderstood. Ok.

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