C# Multi-dimension Array

// Two-dimensional array.  
int[,] array2D = new int[,] 
{ 
     { 1, 2 }, 
     { 3, 4 }, 
     { 5, 6 }, 
     { 7, 8 } 
};

// A similar array with string elements. 
string[,] array2Db = new string[3, 2] 
{ 
     { "one", "two" }, 
     { "three", "four" }, 
     { "five", "six" }                                   
};  

// Three-dimensional array. 
int[, ,] array3D = new int[,,] 
{ 
     { { 1, 2, 3 }, { 4, 5, 6 } },                               
     { { 7, 8, 9 }, { 10, 11, 12 } } 
}; 

 // The same array with dimensions specified. 
int[, ,] array3Da = new int[2, 2, 3] 
{ 
     { { 1, 2, 3 }, { 4, 5, 6 } },                                               
     { { 7, 8, 9 }, { 10, 11, 12 } } 
}; 

Initializing Two-Dimensional Arrays

int [,] a = new int [3,4] {
     {0, 1, 2, 3} ,   /*  initializers for row indexed by 0 */    
     {4, 5, 6, 7} ,   /*  initializers for row indexed by 1 */    
     {8, 9, 10, 11}   /*  initializers for row indexed by 2 */
 };

Accessing Two-Dimensional Array Elements

class MyArray {       
     static void Main(string[] args) {          
     /* an array with 5 rows and 2 columns*/          
     int[,] a = new int[5, 2] {{0,0}, {1,2}, {2,4}, {3,6}, {4,8} };          
     int i, j;                    

     /* output each array element's value */          
     for (i = 0; i < 5; i++) {                          
          for (j = 0; j < 2; j++) {                
               Console.WriteLine("a[{0},{1}] = {2}", i, j, a[i,j]);                
          }         
     }
          
     Console.ReadKey();       
     }    
}

Difference Between Length, Count, Rank

• Length: Total number of elements in an array
• LongLength: Same as Length, but returned as long (in case it’s >= 2³¹)
• Count(): LINQ extension method that works with other collection types as well
• Rank: Number of dimensions in array (always 1 for vectors). Only in .NET 3.5+.
• GetLength(), GetLongLength(): Length of a certain dimension of an array
• GetLowerBound(): Starting index of a certain dimension of an array; always 0 for vectors
• GetUpperBound(): Ending index of a certain dimension of an array; always Length - 1 for vector

string[,] a = {
{“0”, “1”, “2”},
{“0”, “1”, “2”},
{“0”, “1”, “2”},
{“0”, “1”, “2”},
};

// a.Length = 12

Use Array.Rank to get number of dimensions and then use Array.GetLength(int dimension) to get the length of a specific dimension.