C# How can I check overlapping ranges?-CodePudding

I have the following ranges in database. I am trying to check if there is an overlapping range on editing existing records.

Range looks like as follows

I used the following code to check overlapping ranges.

var allRanges = await _dlRangesService.GetAllRanges();
var isOverlapping = allRanges.Any(r => r.RangeStart <= rangeToUpdate.RangeStart && rangeToUpdate.RangeStart <= r.RangeEnd && rangeToUpdate.ID != r.ID) ||
                    allRanges.Any(r => r.RangeStart <= rangeToUpdate.RangeEnd && rangeToUpdate.RangeEnd <= r.RangeEnd && rangeToUpdate.ID != r.ID);

and I added the following condition to through validation on save

if (isOverlapping)
    ModelState.AddModelError("Range", "Range overlaps with existing Range.");

but when I edit the first range in pic above 10000 - 10000 to 10000 - 22000 it allows me to save.

I also tried the following, in this case it won't let me save changes even if there is no overlapping range in the database. but it works on creating a new record.

 var allRanges = await _dlRangesService.GetAllRanges();
 var isOverlapping = allRanges.Any(r => r.RangeStart <= rangeToUpdate.RangeStart && rangeToUpdate.RangeStart <= r.RangeEnd) ||
                     allRanges.Any(r => r.RangeStart <= rangeToUpdate.RangeEnd && rangeToUpdate.RangeEnd <= r.RangeEnd);

Any help?

CodePudding user response：

Of the following possibilities for overlapping ranges;

1)
   [        existing range ]
          [ modified range        ]
2)
          [ existing range        ]
   [        modified range ]
3)
   [        existing range        ]
          [ modified range ]
4)
          [ existing range ]
   [        modified range        ]

Your test was not handling case 4.

Rather than testing if a range contains the start or end of another range. You need to test that both of these cases are true;

1)
        ... range 1 ]
          [ range 2 ...
2)
          [ range 1 ...
        ... range 2 ]

eg;

   r.RangeStart <= rangeToUpdate.RangeEnd 
&& r.RangeEnd   >= rangeToUpdate.RangeStart