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How to: Iterate Over Arrays with for each

 

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The latest version of this topic can be found at How to: Iterate Over Arrays with for each.

This topic shows how to use the for each, in keyword on different types of arrays.

This sample shows how to use for each on array of reference types. Note that if any dimension of a multi dimensional array is zero, the for each loop will not iterate over the array.

// for_each_arrays.cpp  
// compile with: /clr  
using namespace System;  
ref struct MyClass {  
   void Test() { Console::WriteLine("in MyClass"); }  
};  
  
ref struct MyClass2 {  
   void Test() { Console::WriteLine("in MyClass2"); }  
};  
  
int main() {  
   array<MyClass ^> ^ MyArray = gcnew array<MyClass ^>(2);  
  
   int i = 0;  
   for each ( MyClass ^ c in MyArray ) {  
      Console::Write("{0} = ", i++);  
      c -> Test();  
   }  
  
   Console::WriteLine();  
  
   array< MyClass2 ^, 2 > ^ MyArray2 = gcnew array< MyClass2 ^, 2 >(2, 2);  
   i = 0;  
   for each ( MyClass2 ^ c in MyArray2 ) {  
      Console::Write("{0} = ", i++);  
      c -> Test();  
   }  
  
   array< MyClass2 ^, 2 > ^ MyArray3 = gcnew array< MyClass2 ^, 2 >(2, 0);  
   i = 0;  
   for each ( MyClass2 ^ c in MyArray3 ) {  
      Console::Write("{0} = ", i++);  
      c -> Test();  
   }  
}  

0 = in MyClass  
1 = in MyClass  
  
0 = in MyClass2  
1 = in MyClass2  
2 = in MyClass2  
3 = in MyClass2  

This sample shows for each iterating over a ArrayList, which implements IEnumerable.

// for_each_arrays_2.cpp  
// compile with: /clr  
using namespace System;  
using namespace System::Collections;  
  
int main() {  
   int retval = 0;  
  
   ArrayList ^ arr = gcnew ArrayList();  
   arr->Add(10);  
   arr->Add(20);  
   arr->Add(30);  
  
   for each ( int c in arr )  
      retval += c;  
   Console::WriteLine(retval);  
}  

This sample shows how to iterate over an array of arrays.

// for_each_arrays_3.cpp  
// compile with: /clr  
using namespace System;  
  
#define ARRAY_SIZE 2  
  
int main() {  
   int i, j;  
  
   // Declares an array of managed arrays of Int32.  
   array< array< Int32 > ^ > ^ IntArray = gcnew array<array< Int32 > ^>(ARRAY_SIZE);  
  
   for (i = 0 ; i < ARRAY_SIZE ; i++) {  
      IntArray[i] = gcnew array< Int32 >(ARRAY_SIZE);  
         for ( int j = 0 ; j < ARRAY_SIZE ; j++ )   
            IntArray[i][j] = i + 10;  
   }  
  
   for (i = 0 ; i < ARRAY_SIZE ; i++)  
      for (int j = 0 ; j < ARRAY_SIZE ; j++)  
         Console::WriteLine("IntArray[{0}] = {1}", i, IntArray[i][j]);  
   Console::WriteLine();  
  
   for each (array<Int32> ^ xyz in IntArray)  
      for each ( int c in xyz )  
         Console::WriteLine(c);  
}  

IntArray[0] = 10  
IntArray[0] = 10  
IntArray[1] = 11  
IntArray[1] = 11  
  
10  
10  
11  
11  

for each, in

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