The syntax is slightly different but what is the difference between them.
public static string[][] str1 = { new string[] { Total, "N2" }};
public static string[,] str2 = { { Total, "N2" } };
What are the guidelines for the use of each?
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The first one is "jagged" - an array of references to arrays.Lyubomyr Shaydariv– Lyubomyr Shaydariv2016-02-07 10:13:47 +00:00Commented Feb 7, 2016 at 10:13
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6Have a look at this answer.TVOHM– TVOHM2016-02-07 10:14:46 +00:00Commented Feb 7, 2016 at 10:14
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3 Answers
Have a look here: https://msdn.microsoft.com/en-us/library/2s05feca.aspx
Basically, the difference is how the memory is allocated. [,] notation will allocate all of the needed memory in one block, while [][] notation will allocate an array of pointers to arrays, where each array is allocated separately and not necessarily next to the others
2 Comments
"an array of pointers to arrays" - that depends on how its used- the elements might be unitialised. Also, in c# the term "pointer" is not used commonly and should not be a synonym for reference. "A jagged array is an array of arrays, and therefore its elements are reference types and are initialized to null"
In the examples you quoted:
public static string[][] str1 = { new string[] { Total, "N2" }};
public static string[,] str2 = { { Total, "N2" } };
The first one is an array of arrays (Jagged Array). Each entry can point to an array of string.
The second one is a normal 2 dimensional array (Multi Dimensional Array).
Comments
In a nutshell , [,] is a 2d array allocated all at once, while [][] is an array of arrays thus memory allocation is gradual- the initialization syntax (as you pointed out) is different also.
One more important difference is that in a [][] type you can define each 'row' of a different size. which you can't do in [,] which is in a way a C# representation of a Matrix.
