Chapter107:Indexer

Section107.1:Asimpleindexer

classFoo

{

privatestring[]cities=new[]{“Paris”,”London”,”Berlin”};

publicstringthis[intindex]

{

get{

returncities[index];

}

set{

cities[index]=value;

}

}

}

Usage:

varfoo=newFoo();

//accessavalue

stringberlin=foo[2];

//assignavalue

foo[0]=”Rome”;

ViewDemo

Section107.2:Overloadingtheindexertocreatea SparseArray

Byoverloadingtheindexeryoucancreateaclassthatlooksandfeelslikeanarraybutisn’t.ItwillhaveO(1)getand set methods, can access an element at index 100, and yet still have the size of the elements inside of it. The SparseArray class

classSparseArray

{

Dictionary<int,string>array=newDictionary<int,string>();

publicstringthis[inti]

{

get

{

if(!array.ContainsKey(i))

{

returnnull;

}

returnarray[i];

}

set

{

if(!array.ContainsKey(i))

array.Add(i,value);

}

}

}

Section107.3:Indexerwith2argumentsandinterface

interfaceITable{

//anindexercanbedeclaredinaninterface

objectthis[intx,inty]{get;set;}

}

classDataTable:ITable

{

privateobject[,]cells=newobject[10,10];

///<summary>

///implementationoftheindexerdeclaredintheinterface

///</summary>

///<paramname=”x”>X-Index</param>

///<paramname=”y”>Y-Index</param>

///<returns>Contentofthiscell</returns>

publicobjectthis[intx,inty]

{

get

{

returncells[x,y];

}

set

{

cells[x,y]=value;

}

}

}