2-Dimensional Arrays

We can declare 2-Dimensional arrays by using the following statement:

    Dim arrayName(r,c) As Type

Where arrayName is the name of the array you have created and Type is the array's type. The subscripts r and c represent the Row and Column of the array.

So we could declare an array as type double to hold students' grades:

    Dim grades(3,3) As Double
    'Four students with four grades

This creates a 4x4 matrix with rows and columns starting at 0 and ending at 3:

    0   1   2   3
  +---+---+---+---+
0 |   |   |   |   |
  +---+---+---+---+
1 |   |   |   |   |
  +---+---+---+---+
2 |   |   |   |   |
  +---+---+---+---+
3 |   |   |   |   |
  +---+---+---+---+

We can set any cell in the array by issuing a call such as:

    grades(1,1) = 90
    grades(3,0) = 99
    grades(1,0) = 100

With the above code our resulting matrix will look like:

    0   1   2   3
  +---+---+---+---+
0 |   |   |   |   |
  +---+---+---+---+
1 |100| 90|   |   |
  +---+---+---+---+
2 |   |   |   |   |
  +---+---+---+---+
3 |99 |   |   |   |
  +---+---+---+---+

If we wanted to set all the cells to a particular value, such as 0 for example, we would have to use a nested loop:

    For i As Integer=0 To 3
      For j As Integer=0 To 3
          grades(i,j) = 0
      Next
    Next

We can also declare the 2-dimensional array without a size as we can with regular arrays:

    Dim arrayName(,) As Type
    Dim array2(,) As Type = {{ROW0},{ROW1},{ROW2},...,{ROWm}}

    ReDim arrayName(r,s)
    ReDim Preserve arrayName(r,s)

Real Examples:

    Dim grades(,) = {{99,50,80},{100,80,70},{90,88,90}}
    ReDim Preserve grades(3,4)

GetUpperBound

There are two different GetUpperBound calls for 2-dimensional arrays:

    arrayName.GetUpperBound(0)
    arrayName.GetUpperBound(1)

The first call gives you the upperbound on the number of rows, while the second one gives you the upperbound on the number of columns.