c# operator ! cannot be applied

Question

i wonder why ! cannot be applied

this is my code :

  for (int i = 0; i < rowcol.GetLength(0); i++)
            {
                for (int j = 0; j < rowcol[i].GetLength(0); j++)
                {

                     var top = !((rowcol[i-1][j])) ? rowcol[i-1][j] : '';
                    var bottom = !(rowcol[i+1][j]) ? rowcol[i+1][j] : '';
                    var left = !(rowcol[i][j-1]) ? rowcol[i][j-1] : '';
                    var right = !(rowcol[i][j+1]) ? rowcol[i][j+1] : '';


                }
            }

i have a jagged array that , i am reading the values from a textfile . i am having error with operator ! cannot be applied to string , but i and j is int , , yes rowcol is reading a string from a textfile .

please tell me if u need the full code . Help is appreciated thanks

Answer 1

The issue is that rowcol[i-1][j] is a string, and ! cannot be applied to a string. The same applies for each of your four lines.

Edit: If your goal is to check that the string is not null or empty, try instead:

var top = !(String.isNullOrEmpty(rowcol[i - 1][j])) ? rowcol[i - 1][j] : '';

and so on, or, if you know that the string will be null and not empty,

var top = (rowcol[i - 1][j]) != null) ? rowcol[i - 1][j] : '';