C# Advanced L02-Operator Overloading+Indexers+UD Conversion

Mohammad Shaker
mohammadshaker.com
@ZGTRShaker
2011, 2012, 2013, 2014
C# Advanced
L02-Operator Overloading, Indexers &
User-Defined Conversion

Operator Overloading
•Good implementation
Car mySedan= new Car();
Garage parkingGarage= new Garage(); mySedan= mySedan+ parkingGarage; // park car in the garage

•How to add two Matrices?

Matrix result = mat1.Add(mat2);

Matrix result = Matrix.Add(mat1, mat2);

Matrix result = mat1 + mat2;

•So, how can we implement it?
–Dot product
public static Matrix operator *(Matrix mat1, Matrix mat2) { // dot product implementation}

–Dot product
Return Type
Keyword
Must be static
Operator
Arguments

–Dot product
Return Type
Keyword
Must be static
Operator
Arguments
Why?

classMatrix
{
publicconstintDimSize=3;
private double[,] m_matrix= new double[DimSize, DimSize];
// allow callers to initialize
public double this[intx, inty]
{
get { return m_matrix[x, y]; }
set { m_matrix[x, y] = value; }
}
// let user add matrices
public static Matrix operator +(Matrix mat1, Matrix mat2)
{
Matrix newMatrix= new Matrix();
for (intx = 0; x < DimSize; x++)
for(inty = 0; y < DimSize; y++)
newMatrix[x, y] = mat1[x, y] + mat2[x, y];
return newMatrix;
}
}

classMatrix
{
privatedouble[,] m_matrix=newdouble[DimSize, DimSize];
publicdoublethis[intx, inty]
{
get{ returnm_matrix[x, y]; }
set{ m_matrix[x, y] =value; }
}
{
return newMatrix;
}
}

classMatrix
{
publicdoublethis[intx, inty]
{
get{ returnm_matrix[x, y]; }
set{ m_matrix[x, y] =value; }
}
{
return newMatrix;
}
}
Operator Overloading Declaration

•Performing the operator, just write the following:
Matrix mat1 = new Matrix();
Matrix mat2 = new Matrix();
// perform operation and print out results
Matrix mat3 = mat1 + mat2;

classMatrix
{
{
}
{
return newMatrix;
}
}

Indexers
•Indexers are really easy!
•They allow your class to be used just like an array. On the inside of a class, you manage a collection of values any way you want.
•They are like properties
publicstringthis[intpos] { get{ returnmyData[pos]; } set{ myData[pos] =value; } }

Operator Overloading and Indexers
classMatrix
{
{
}
{
return newMatrix;
}
}

User-Defined ConversionThe Concept

•We can’t do this out-of-the-box!
•But in a moment we will. This is a User-defined conversion. Because we are casting our type (Car) to something else.
•There’re two types of conversion:
–implicit
•which occur automatically when required, saying: intcarWeight= car;
–explicit
•which require a cast to be called, saying: intcarWeight= (int)car;
•All conversions must bestatic, and must either take the type the conversion is defined on, or return that type.
Car car= new Car();
intcarWeight= (int)car;

•Let’s have the following user-defined class
public class MagicNumber
{
public intNumber { get; set; }
public boolIsMagic{ get; set; }
}

•And let’s say we want to do sthlike this:
{
}
intnum= 3;
MagicNumbermagicNumber= num;

•We should then add the following staticmember
{
}
intnum= 3;
public static implicit operator MagicNumber(intvalue)
{
return new MagicNumber() { Number = value, IsMagic= false };
}

{
}
intnum= 3;
{
}
Means a user-defined conversion

{
}
intnum= 3;
{
}
Implicit Because we want to do this
Not explicit like:
MagicNumbermagicNumber= (MagicNumber)num;

{
}
intnum= 3;
{
}
Means a user-defined conversion from intto MagicNumber(the return type)

Now let’s do this:
MagicNumbermagicNumber= new MagicNumber() { Number = 3, IsMagic= true };
intaNumber= (int)magicNumber;

•To do this:
MagicNumbermagicNumber= new MagicNumber() { Number = 3, IsMagic= true };
intaNumber= (int)magicNumber;
public static explicitoperator int(MagicNumbermagicNumber)
{
return magicNumber.Number;
}

C# Advanced L02-Operator Overloading+Indexers+UD Conversion

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