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C# Method Return Structure by Reference

Posted on 2010-11-11
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Last Modified: 2012-05-10
Hi,

Is it possible to return a structure by reference?

Example:
public struct myStruct
{
string foo;
string bar;
}

public myStruct[] Instances;
Instances = new myStruct[1];
Instances[0].foo = "Hello";
Instances[1].bar = "World";

public myStruct getInstance()
{
return Instances[0];
}

myStruct instance = getInstance();

This will return a copy of the structure, I want it to return the reference to it so I can do this:
myStruct instance = getInstance();
instance.foo = "Source";
instance.bar = "Code";

I know I can pass instance as a reference variable:
myStruct instance = new MyStruct();
getInstance(ref instance);

But I don't want to do this if I don't have to.

Many thanks,
Storm
0
Comment
Question by:Cyber-Storm
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6 Comments
 
LVL 52

Assisted Solution

by:Carl Tawn
Carl Tawn earned 300 total points
ID: 34110227
The only way I can thing of doing it would be to return a pointer, but i don't think you want to be doing that.
0
 
LVL 18

Accepted Solution

by:
Richard Lee earned 450 total points
ID: 34110318
The simple answer is no. Are there ways around it? maybe.

http://msdn.microsoft.com/en-us/library/dd183752.aspx

Notice instead of using MyStruct for the array construction I am using object. I am boxing the structure inside and object therefore the object are moved around by reference.

DaTribe
class Program
{
	public struct myStruct
	{
		public string foo;
		public string bar;
	}

	public static object[] Instances;

	public static object getInstance()
	{
		return Instances[0];
	}

	static void Main(string[] args)
	{
		Instances = new object[2];

		Instances[0] = new myStruct {foo = "Hello"};
		Instances[1] = new myStruct {bar = "World"};

		var instance = getInstance();
		Console.WriteLine(object.ReferenceEquals(instance, Instances[0]));
		Console.ReadKey();
	}
}

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0
 

Author Comment

by:Cyber-Storm
ID: 34110321
Yeah, wouldn't want to go the unsafe route, how would I fix the below then?
public struct myStruct
{
string foo;
string bar;
}

public myStruct[] Instances;
Instances = new myStruct[1];
Instances[0].foo = "Hello";
Instances[1].bar = "World";

public int getInstanceID()
{
return 0;
}

Now am forced to do this
Instances[getInstanceID()].foo = "Source";
Instances[getInstanceID()].bar = "Code";
but I want to do something like this instead
myStruct instance = Instances[getInstanceID()];

so that I can do this:
instance.foo = "Source";
instance.bar = "Code";
Thanks
0
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Author Comment

by:Cyber-Storm
ID: 34110382
Thanks DaTribe,
We posted at the same time so I didn't see yours.  I wouldn't want to go the object route as it's concidered a "dirty" solution.  But I fully understand your logic and while I know doing it this way would work, I was hoping for a "cleaner" solution and was reserving that as my last resort if I didn't come right here.
0
 
LVL 18

Expert Comment

by:Richard Lee
ID: 34110449
The link I provided explains that it is not possible for two structs to have the same address so I do not think the approach you require is possible.

http://msdn.microsoft.com/en-us/library/dd183752.aspx

DaTribe
0
 

Author Closing Comment

by:Cyber-Storm
ID: 34111629
I implemented a class instead of a structure and exposed the variables as automatic properties, I think this is the cleanest and most elegant solution in this case.

Both good options you guys put forth as well, thanks guys.
0

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