difference between double[*,*] to double[][] in c#

Question

i used

double [,] marks=new double[26,5] 
int[] function = object.verify(marks) 

public void verifymarks(double[][] marks)

error i get is cannot convert from double[,] to double[][] i tried to search in the internet but couldnot find any solution. I have just began to use c#. Please Help. THankx in advance

Answer 1

double[][] is jagged. It's literally an array of arrays.

double[,] is multidimensional. It gets special compiler treatment.

They have different memory layouts. double[][] is an array which holds references to the other arrays, while double[,] is laid out single-dimensionally for easier use.

Another difference is what data they can hold. A jagged array can be like this:

1231243245345345345345
23423423423423
2342342343r234234234234234234
23423

While a multidimensional array has to be a perfect table, like this:

34534534534534
34534534534533
34534534534534
34534534534545

A way to get around it would be to use nullable ints.

Now, to solve your problem:

Change your method signature to public void verifymarks(double[,] marks) and in the method change anything that uses marks[x][y] to marks[x,y].

Answer 2

double[][] is called a Jagged array. It is an array of array (the same way you could create a list of list). With this structure you can specify a different size for each sub-array.

For exemple:

double[][] jaggedArray = new double[2][];
jaggedArray[0] = new double[5];
jaggedArray[1] = new double[151];

The other writing double[,] is a 2D array (Multidimensional array in general). You can see it as a table.

A very handy feature of multidimensional array is the initialization:

string[,] test = new string[3, 2] { { "one", "two" }, 
                                    { "three", "four" },
                                    { "five", "six" } };