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linq groupjoin using lambda with a where clause

Posted on 2013-01-13
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Last Modified: 2013-11-05
I need to add a join using Lambda if I have a further parameter available that will also be used in a where clause.

This is my original linq code, it works just fine...

    var tagList =   from t in dc.Tags
    join b in dc.Businesses on t.BusinessId equals b.BusinessId
            where t.IsActive == true
            where b.IsActive == true
            orderby t.AdImage descending
            select new TagItem
            {
                    tagName = t.Name.Replace("\"", ""),
                    tagImage = tagImagePath + t.AdImage.Replace("\"", ""),
                    tagDescription = t.Description.Replace("\"", "")
            };

My problem is I'm not sure of the exact format for adding a new object [table] MemberTagLysts using Lambda and then how the where clause should be created when I have a lystId available...

This is not quite right....

            if (!string.IsNullOrEmpty(lystId))
            {
                            tagList = (IQueryable<TagItem>)tagList.GroupJoin(dc.MemberTagLysts, a => a.tagId, b => b.TagId, (a, b) => new { a, b });
            }
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Question by:Rob Gaudet
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4 Comments
 
LVL 42

Expert Comment

by:Meir Rivkin
ID: 38774007
can u explain what kind of join you wish to apply with MemberTagLysts table?
0
 
LVL 42

Expert Comment

by:Meir Rivkin
ID: 38774017
first u need to add tagId in your initial linq query:
.
.
.select new TagItem
            {
tagId = t.tagId,
                    tagName = t.Name.Replace("\"", ""),
                    tagImage = tagImagePath + t.AdImage.Replace("\"", ""),
                    tagDescription = t.Description.Replace("\"", "")
            };

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now try run this:
   tagList = (IQueryable<TagItem>)tagList.GroupJoin(dc.MemberTagLysts, a => a.tagId, b => b.TagId, (a, b) => new { a, b });

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0
 

Author Comment

by:Rob Gaudet
ID: 38779233
Sorry, tagid was in the initial query, I shortened the values to save space and pulled it out..

Your suggestion...

tagList = (IQueryable<TagItem>)tagList.GroupJoin(dc.MemberTagLysts, a => a.tagId, b => b.TagId, (a, b) => new { a, b });

....returned this error.

Unable to cast object of type 'System.Data.Linq.DataQuery`1[<>f__AnonymousType6`2[TagItem,System.Collections.Generic.IEnumerable`1[MemberTagLyst]]]' to type 'System.Linq.IQueryable`1[TagItem]'.
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LVL 42

Accepted Solution

by:
Meir Rivkin earned 1500 total points
ID: 38779580
just
var group = tagList.GroupJoin(dc.MemberTagLysts, a => a.tagId, b => b.TagId, (a, b) => new { a, b });

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