What is wrong with the definition of this Struct type

Question

I have defined my struct like this:

struct Test
{
    private string assayName;
    public string AssayName { get; set; }

    private string oldUnitName;
    public string OldUnitName { get; set; }

    private string newUnitName;
    public string NewUnitName { get; set; }

    public Test(string name, string oldValue, string newValue)
    {
        assayName = name;
        oldUnitName = oldValue;
        newUnitName = newValue;
    }

}

but it gives me the following error:

"Error 13 Backing field for automatically implemented property 'EnterResults.frmApplication.Test.NewUnitName' must be fully assigned before control is returned to the caller. Consider calling the default constructor from a constructor initializer."

Answer 1

Well, there are two issues really:

1.Your using automatic properties, but then also providing fields, there is no wiring between the two.

2.When you use automatic properties, because this is a struct, they have to be initialised first. You can do this with a call to the default constructor. So a revised version would be:

struct Test
{
    public Test(string name, string oldValue, string newValue)
        : this()
    {
        AssayName = name;
        OldUnitName = oldValue;
        NewUnitName = newValue;
    }

    public string AssayName { get; private set; }
    public string OldUnitValue { get; private set; }
    public string NewUnitValue { get; private set; }
}

Answer 2

You aren't actually doing anything with the properties. Try this:

struct Test 
{ 
    public string AssayName { get; set; } 
    public string OldUnitName { get; set; } 
    public string NewUnitName { get; set; } 

    public Test(string name, string oldValue, string newValue) : this()
    { 
        AssayName = name; 
        OldUnitName = oldValue; 
        NewUnitName = newValue; 
    } 
} 

I think this has to do with struct initialization. Note the call to the default constructor I added seems to make it happy :)

"Seems to make it happy" - how dumb is that. I poked around for the real answer which is tied to how structs are initialized. Calling the default constructor insures fields are initialized before the struct is used.