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How to linq join with groups?

Anurag Sharma 2680 04-Nov-2014

Hej, i've got a problem with linq expression. I Would like to perform join with groups of some set. This is basicly what I need:

var f = new IEnumerable<SomeClass> { ... };
var rows = new IEnumerable<SomeOtherClass> { ... };
var makedGroups = rows.GroupBy(row => row.SomeId);
var groupsJoined = (from row in makedGroups
    join allocQuant in f on row.Key.Value equals allocQuant.SomeId into gj
    select gr => new { Count = gr.Count(), Group = gj });

error is: Error 202 The type of one of the expressions in the join clause is incorrect. Type inference failed in the call to 'Join'.

How to write this expression properly?

c# join

Updated on 04-Nov-2014

Anurag Sharma

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David Miller

04-Nov-2014

No longer have access to the range variables used in the initial from. That is, we can no longer talk about p or bp, you can only talk about pg.

Now, pg is a group and so contains more than one product. All the products in a given pg group have the same SomeId (since that's what you grouped by), but I don't know if that means they all have the same BaseProductId.

To get a base product name, you have to pick a particular product in the pg group (As you are doing with SomeId and CountryCode), and then join to BaseProducts.

var result = from p in Products                         
 group p by p.SomeId into pg                         
 // join *after* group
 join bp in BaseProducts on pg.FirstOrDefault().BaseProductId equals bp.Id         
 select new ProductPriceMinMax { 
       SomeId = pg.FirstOrDefault().SomeId, 
       CountryCode = pg.FirstOrDefault().CountryCode, 
       MinPrice = pg.Min(m => m.Price), 
       MaxPrice = pg.Max(m => m.Price),
       BaseProductName = bp.Name  // now there is a 'bp' in scope
 };

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How to linq join with groups?

Anurag Sharma

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