C# Finding the maximum value of a string with linq

Question

This is what I have and it keeps returning null.

It doesn't recognize the Convert.toInt32 when I add a where statement

var maxTopID = (from max in dbcontext.Topics.Local
               select max.TopicID).Max();

where is your `where` statement? where is your `Covnert.ToInt32`? — King King, Dec 05 '13 at 06:11
Do you have values in TopicId ? what is the data type of TopicId ? — SpiderCode, Dec 05 '13 at 06:12
with the where statement it read var maxTopID = (from max in dbcontext.Topics.Local where Convert.ToInt32(max.TopicID) select max.TopicID).Max(); — , Dec 05 '13 at 06:13

Edper · Accepted Answer · 2013-12-05T06:26:36.487

4

How about converting the TopicID in SELECT and use String.IsNullOrEmpty() to remove empty string, like:

 var maxTopID = (from max in dbcontext.Topics.Local
                 where !String.IsNullOrEmpty(max.TopicID)
                 select Convert.ToInt32(max.TopicID)).Max();

See the Demo

edited Dec 05 '13 at 06:26

answered Dec 05 '13 at 06:19

Edper

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Does LINQ to SQL support `String.IsNullOrEmpty()`? I am pretty it doesn't support `String.IsNullOrWhiteSpace()`, but does it support the former one I am not sure. – Sнаđошƒаӽ Nov 19 '17 at 10:46
Did you check the **Demo** link? That's straight from a C# compiler. Also `String.IsNullOrEmpty()` could be use anywhere as long as you're testing a value if it is `null` or empty. – Edper Nov 19 '17 at 14:05
I visited that link, but didn't bother to run it, because that has nothing to do with my question. To be explicit, that doesn't involve LINQ to SQL. Nevermind, I will check myself tomorrow, and let you know, if I remember that is. After all, the OP isn't about LINQ to SQL itself. – Sнаđошƒаӽ Nov 19 '17 at 17:51

SpiderCode · Answer 2 · 2013-12-05T06:19:41.827

1

Check for the null condition as mentioned in below query

var maxTopID = (from max in dbcontext.Topics.Local
                 where  max.TopicId != null
                 select max.TopicID).Max();

edited Dec 05 '13 at 06:19

answered Dec 05 '13 at 06:14

SpiderCode

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score 1 · Answer 3 · answered Dec 05 '13 at 06:17

I think you are saying that TopicID is string and you want to convert it to int

var list= (from max in dbcontext.Topics.Local
                     where  max.TopicId != null
                     select max.TopicID).ToList();

int max=0;

if (list.Count() !=0)
max=list.Select(int.Parse).ToList().Max();

max will contain max value from list which is converted to list of integer

C# Finding the maximum value of a string with linq

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