What does => operator pointing from field or a method mean? C#

Question

I've seen an operator => used in the following example:

public int Calculate(int x) => DoSomething(x);

or

public void DoSoething() => SomeOtherMethod();

I have never seen this operator used like this before except in lamba expressions.

What does the following do? Where, when should this be used?

@StephenBrickner: An expression-bodied member. It's not an assignment. — Joey, Sep 12 '16 at 15:20
Sorry, I should have set the duplicate to http://stackoverflow.com/questions/31764532/what-is-the-assignment-in-c-sharp-in-a-property-signature — Jon Skeet, Sep 12 '16 at 15:20

score 9 · Accepted Answer · answered Sep 12 '16 at 15:19

9

These are Expression Body statements, introduced with C# 6. The point is using lambda-like syntax to single-line simple properties and methods. The above statements expand thusly;

public int Calculate(int x)
{
    return DoSomething(x);
}

public void DoSoething()
{
    SomeOtherMethod();
}

Notably, properties also accept expression bodies in order to create simple get-only properties:

public int Random => 5;

Is equivalent to

public int Random
{
    get
    {
        return 5;
    }
}

answered Sep 12 '16 at 15:19

David

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It's not a statement, but a member declaration. – Joey Sep 12 '16 at 15:20
This poses a new question. What does thusly mean? thus => thusly ? – joym8 Dec 19 '21 at 02:09

Luis Lavieri · Answer 2 · 2016-09-12T15:22:14.230

5

Take a look at this Microsoft Article. It's a C# 6.0 feature where properties have no statement body. You could use them to get methods, or single line expressions. For example:

public override string ToString() => string.Format("{0}, {1}", First, Second);

edited Sep 12 '16 at 15:22

answered Sep 12 '16 at 15:20

Luis Lavieri

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@Joey true. Fixed wording – Luis Lavieri Sep 12 '16 at 15:23
Wonderful example of not only "what is this" but "how is this useful?" – David Sep 12 '16 at 18:45

score 4 · Answer 3 · answered Sep 12 '16 at 15:19

A new feature in C# 6.0 called an expression body.

It is shorthand to write a single line of code with a return value.

For example

int GetNumber() => 1;

Is an expression body statement which is the same as:

int GetNumber()
{
    return 1;
}

You can read more here

score 1 · Answer 4 · answered Sep 12 '16 at 15:17

It's a new shorthand syntax in C# 6.

In your first example it's defining a public method, Calculate(int x) whose implementation is defined within DoSomething(x).

An equivalent definition would be:

class SomeClass {

    public int Calculate(int x) { return DoSomething(x); }

    protected int DoSomething(int x) { ... }
}

What does => operator pointing from field or a method mean? C#

4 Answers4