Structs cannot contain explicit parameterless constructors

Question

I'd like to define a struct that includes StopWatch and then an array of struct.

    struct SWExecutionTime
    {
        public Stopwatch swExeTime;
        public int intSWRecCount;
        public double dblSWResult;
    }

    SWExecutionTime[] SWExeTime = new SWExecutionTime[10];

It shows run-time error System.NullReferenceException when I try to do this:

    SWExeTime[0].swExeTime.Start();

The initial value of intSWRecCount and dblSWResult are zero, so I don't need to have a constructor to initialize these variables. The only variable that needs initialization is swExeTime (apparently). C# also shows the error Structs cannot contain explicit parameterless constructors when I use constructor without any input parameter.

How can I fix this?

`new SWExecutionTime()` only instantiates the struct; it does not create a new stopwatch object within the struct. If you want to do that, write a constructor for the struct, or provide a default instantiation. — Robert Harvey, Oct 13 '15 at 21:12
I have no idea what that means. Without some sort of construction, there's no hope of having a stopwatch object in there. Remember, `int` and `double` are primitive types; the compiler can assume a default value of zero for them. The same is not true of the StopWatch class. — Robert Harvey, Oct 13 '15 at 21:14
Alternatively, use a `class` instead of a `struct`. Then you can write your parameterless constructor without the compiler complaining. — Robert Harvey, Oct 13 '15 at 21:16

score 3 · Accepted Answer · answered Oct 13 '15 at 21:18

3

Use a class, why are you stuck on structs?

class SWExecutionTime
{
    public Stopwatch SWExeTime { get; } = new Stopwatch();
    public int SWRecCount { get; } = 0;
    public double SWResult { get; } = 0;
}

Also, follow best practices for naming.

answered Oct 13 '15 at 21:18

Jonesopolis

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Structs cannot contain explicit parameterless constructors

1 Answers1