CODEWITHSUNDEEP
sql-serverlinqentity-frameworktype-conversion
Khushi
Khushi

Reputation: 1051

Getting an type conversion error while using linq in entity framework

I am trying to get the data from SQL Server database.

I have a table called Standard in my database. It has three columns StandardID, StandardName, and Description.

I have a combobox in which I fill the values of StandardName

Here is the code :

Using db As New SchoolDBEntities
    ComboSelectStandardToEdit.DataSource = db.Standards.ToList()
    ComboSelectStandardToEdit.ValueMember = "StandardID"
    ComboSelectStandardToEdit.DisplayMember = "StandardName"
End Using

Now I have 2 textboxes called txtStandardName and txtDescription.

I want to fill the values of these 2 textboxes based on selected StandardName from the combobox.

Here is the code I tried :

Using db As New SchoolDBEntities
            Dim standard = From s In db.Standards
                            Where s.StandardId = CInt(ComboSelectStandardToEdit.SelectedValue)
                            Select s

            txtStandardName.Text = CType(standard, Standard).StandardName
        End Using

but unfortunately I got error :

Unable to cast object of type 'System.Data.Entity.Infrastructure.DbQuery`1[EF_WinForms_VB.Standard]' to type 'EF_WinForms_VB.Standard'.

Upvotes: 0

Views: 162

Answers (2)

Harshil Raval
Harshil Raval

Reputation: 2145

Try using

Dim standard = (From s In db.Standards.AsEnumerable Where s.StandardId = Convert.ToInt32(ComboSelectStandardToEdit.SelectedValue) Select s) .FirstOrDefault

txtStandardName.Text = standard.StandardName

Hope it helps.

Upvotes: 1

Claies
Claies

Reputation: 22323

try using

Dim standard = (From s In db.Standards
    Where s.StandardId = CInt(ComboSelectStandardToEdit.SelectedValue)
    Select s)
    .FirstOrDefault

txtStandardName.Text = standard.StandardName

your Linq query currently is returing a projection which could contain multiple entries. By explicitly requesting the first object of the projection, you won't need to cast your standard before accessing it's value.

Upvotes: 2

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