Convert string to int for sum in linq

Question

I have a column requestAmount that is nvarchar(100).

I need to calculate sum :

int? sum = q.Sum(g => g.requestAmount);

I got this error:

Error 26 Cannot convert lambda expression to delegate type 'System.Func<samtaApplication.DbLayer.tblMaterial,int>' because some of the return types in the block are not implicitly convertible to the delegate return type

How can I convert string to int?

it's nice to know that requestAmount is nvarchar(100), but as you're in an c# object world, you can just say that it's a string ;) — Raphaël Althaus, Dec 04 '13 at 12:32
Enumerable.Sum never returns null. So are you sure you need a `Nullable` ? — Raphaël Althaus, Dec 04 '13 at 12:48

score 5 · Answer 1 · edited Dec 04 '13 at 12:44

5

In linq to entities you can always materialize query first, so you will operate on linq to objects

int? sum = q.AsEnumerable().Sum(g => Int.Parse(g.requestAmount));

Note that it will load whole q from db

EDIT:

if requestAmount is nullable then use:

int? sum = q.AsEnumerable().Sum(g => Convert.ToInt32(g.requestAmount));

Convert.ToInt32 will return 0 when null is passed as parameter

edited Dec 04 '13 at 12:44

Raphaël Althaus

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answered Dec 04 '13 at 12:33

Kamil Budziewski

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Hmmm, and if requestAmount is null ? – Raphaël Althaus Dec 04 '13 at 12:39
@RaphaëlAlthaus there is no information about nullability of this field. If it's nullable nvarchar then we need to use Convert.ToInt32 – Kamil Budziewski Dec 04 '13 at 12:41
Well, for your second version, sum whill never be null, so why use a `Nullable`. Question is not clear on this point, you're right. – Raphaël Althaus Dec 04 '13 at 12:44
Anyway, Enumerable.Sum never returns null... So the second version is perfectly valid... – Raphaël Althaus Dec 04 '13 at 12:47
@RaphaëlAlthaus yeah, only way to return null will be making some if statement and checking if all values are null -> return null / else count sum of non-null values – Kamil Budziewski Dec 04 '13 at 12:49

score 3 · Accepted Answer · answered Dec 04 '13 at 12:31

3

int? sum = q.Sum(g => Int32.Parse(g.requestAmount));

answered Dec 04 '13 at 12:31

Giannis Paraskevopoulos

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score 2 · Answer 3 · answered Dec 04 '13 at 12:34

A string can be null or empty, so, keep it safe using a filter with Where and after it applying and Sum , for sample:

int dummy;
int result = q.Where(g => int.TryParse(g.TryParse(g.requestAmount, out dummy))
              .Sum(g => int.Parse(g.requestAmount.Trim()));

score 0 · Answer 4 · answered Dec 04 '13 at 12:34

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have you tried using the int.TryParse?

answered Dec 04 '13 at 12:34

user1666620

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Convert string to int for sum in linq

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