CODEWITHSUNDEEP
.netvb.netlinqlinq-to-objects
Zabman
Zabman

Reputation: 117

LINQ query throwing a cast exception

I am attempting a LINQ query in a VB.NET WPF solution that bridges two datatables and groups by a Zone.

I am receiving an "Invalid Cast Exception" on these rows:

.MfstCt = ZoneGroup.Count(Function(c) c.Field(Of String)("ConsignmentNumber")), _
.ArticleCt = ZoneGroup.Count(Function(c) c.Field(Of String)("ArticleNumber")) _

The error states:

Conversion from string "B4B0158234" to type 'Boolean' is not valid.

But I don't see any conversion to boolean in my query.

The field ConsignmentNumber is in the mfst table, and the field ArticleNumber is in the article table. I have added the entire query below. Can anyone help advise where I am going wrong with this?

Dim query = _
    From Mfst In tblMFst.AsEnumerable() _
    Join article In tblArticle.AsEnumerable() _
    On Mfst.Field(Of Integer)("PCMSConsignment_ID") Equals _
        article.Field(Of Integer)("PCMSConsignment_ID") _
    Group Mfst By Zone = Mfst.Field(Of String)("PostZone") Into ZoneGroup = Group
    Select New With _
    { _
        Key Zone, _
        .MfstCt = ZoneGroup.Count(Function(c) c.Field(Of String)("ConsignmentNumber")), _
        .ArticleCt = ZoneGroup.Count(Function(c) c.Field(Of String)("ArticleNumber")) _
    }

For Each x In query
    Console.WriteLine(x.Zone, x.MfstCt, x.MfstCt)
Next

EDIT: I have changed code to reflect correct (Of String) and updated the error message being received.

Upvotes: 0

Views: 840

Answers (2)

Jeff B
Jeff B

Reputation: 8982

LINQ's .Count extension method, when it takes a Func predicate requires the function to return a boolean. See the documentation here. The function is there to act as a predicate to chose which elements to count (for example Function(x) x >= 20).

I'm not sure exactly what you're trying to accomplish, but it seems like you should be just do something like ZoneGroup.Count() or if you're trying to match a particular condition ZoneGroup.Count(Function(c) c.IsTheThingWeWant()).

Upvotes: 1

Aaron Palmer
Aaron Palmer

Reputation: 8992

The Linq Count function expects a boolean comparison. You are passing:

.Count(Function(c) c.Field(Of String)("ConsignmentNumber"))

It is trying to return c.Field(Of String)("ConsignmentNumber") as a boolean.

Upvotes: 0

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