如何在linq to sql中计算多个不同的列？

Question

I am struggling with Linq, hence it is a lame question but still .. I have a table with following 4 columns

Pid   SKU    colorid   sizeid
1     'A65102'    38       2
2     'A65102'    38       4
3     'A65102'    38       18

I have to get how many different color and size option are available for this.

In sql, I use to do it by:

select count(distinct [sizeid]) ,count(distinct [colors]) 
from [item_master] 
where sku = 'A65102' 

But in Linq, I can get all the values by

var dd = (from im in db.item_masters 
          where im.sku.Contains("A65102") 
          select new {im.sizeid,im.colors });

But how can I get the count of distinct values for both in single query?

Answer 1

You could use GroupBy :

var distinctCounts = db.item_masters.GroupBy(im => im.sku)
    .Where(grp => grp.Key == "A65102")
    .Select(grp => new { 
        CntSizes  =  grp.Select(im => im.sizeid).Distinct().Count(),
        CntColors =  grp.Select(im => im.colorid).Distinct().Count()
    });

Answer 2

You can use the query that you have as a data source for retrieving this data (especially useful if you would want to use it for other things as well afterwards):

var dd = (from im in db.item_masters 
          where im.sku == "A65102" 
          select new {im.sizeid, im.colors}).ToList();

var numDistinctSizes = dd.Select(x => x.sizeid).Distinct().Count();
var numDistinctColors = dd.Select(x => x.colors).Distinct().Count();