I have two classes A and B and I want to cast an instance of A to B. What's the best way? How Can I make a utility class to perform this task?
public class A
{}
public class B
{}
A good place to start is by reviewing the MSDN documentation on Casting and Type Conversions .
As there's no direct relationship between the two classes, you'll need to write a Conversion Operator . For example:
public class A
{
public int AValue { get; set; }
}
public class B
{
public int BValue { get; set; }
public static explicit operator B(A instanceOfA)
{
return new B { BValue = instanceOfA.AValue };
}
}
You could then write:
A instanceOfA = new A { AValue = 7 };
B instanceOfB = (B)instanceOfA;
// Will output "7"
Console.WriteLine(instanceOfB.BValue);
The documentation I've derived this example from is on MSDN, Using Conversion Operators .
If there was a direct relationship between the two classes, for example B
derives from A
, for example:
public class A
{
public int Value { get; set; }
}
public class B : A
{
public string OtherValueSpecificToB { get; set; }
}
You wouldn't then need any extra code if you wanted to cast from B to A:
B instanceOfB = new B { OtherValueSpecificToB = "b", Value = 3 };
A instanceOfBCastToA = (A)instanceOfB;
// Will output "3";
Console.WriteLine(instanceOfBCastToA.Value);
// Will not compile as when being treated as an "A" there is no "OtherValueSpecificToB" property
Console.WriteLine(instanceOfBCastToA.OtherValueSpecificToB);
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