Kicking around some small structures while answering this post, I came across the following unexpectedly:
The following structure, using an int field is perfectly legal:
struct MyStruct
{
public MyStruct ( int size )
{
this.Size = size; // <-- Legal assignment.
}
public int Size;
}
However, the following structure, using an automatic property does not compile:
struct MyStruct
{
public MyStruct ( int size )
{
this.Size = size; // <-- Compile-Time Error!
}
public int Size{get; set;}
}
The error returned is "The 'this' object cannot be used before all of its fields are assigned to". I know that this is standard procedure for a struct: the backing field for any property must be assigned directly (and not via the property's set accessor) from within the struct's constructor.
A solution is to use an explicit backing field:
struct MyStruct
{
public MyStruct(int size)
{
_size = size;
}
private int _size;
public int Size
{
get { return _size; }
set { _size = value; }
}
}
(Note that VB.NET would not have this issue, because in VB.NET all fields are automatically initialized to 0/null/false when first created.)
This would seem to be an unfortunate limitation when using automatic properties with structs in C#. Thinking conceptually, I was wondering if this wouldn't be a reasonable place for there to be an exception that allows the property set accessor to be called within a struct's constructor, at least for an automatic property?
This is a minor issue, almost an edge-case, but I was wondering what others thought about this...
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