Code builds on vs 2017 but not in vs 2015

Question

After building and testing my solution on Visual Studio 2017 (target framework .NET 4.5, vs + resharper) I run it in production environment with Visual Studio 2015 (same target framework).

In this case I receive syntax error while trying to build it.

For example:

public double Frequency
{
    get => _frequency;
    set 
    {
        if (value > 0)
            _frequency = value;
    }
}

In VS 2015 I get:

" { or ; expected "

Why does this happen?

Answer 1

The specific feature you are using for your get definition (expression-bodied members) is specific to C# version 7.0, as detailed here .

So the reason why your code is not compiling is because VS 2015 uses C# 6.0 and VS 2017 uses C# 7.0.

You can change you get declaration to the following in order to make it compatible with C# 6.0 and the it will build in VS 2015:

get { return _frequency; }

---

Although I have never tried it, after a quick look around the web , it seems it would be possible for you to use C# 7.0 with Visual Studio 2015 if you would prefer that option. Then you should in theory be able to compile your code without making any changes.