C# split string into 2D array : I have .txt file with 10 954 lines in the format of `6,4:10`

I need to load that .txt file with `StreamReader` and split every line at `':'` into 2D array.

To look like this

    [6,4 10]
    [5,2 15]
    [9,3 20]

So i can later on count each column and place it in a particular category.