Updating data linq
The things that are added above are Buttons for Edit, Delete, Update and Cancel which is by default set their enable property to false, this is to prevent users from doing certain actions when the page is loaded in the browser.Aside from that I have also move the form fields inside a Panel control for validation purposes and removed the Read Only attribute for each Text Box.I´m trying to update my Students table record using LINQ to SQL. data types are matched Here is the full Argument Exception: _ Public Class Student Implements System. Guid) If ((_student_id = value) = False) Then Send Property Changing() _student_id = value Send Property Changed("student_id") End If End Set End Property _ Public Property first_name() As String Get Return _first_name End Get Set(By Val value As String) If ((_first_name = value) = False) Then **Send Property Changing()** _first_name = value Send Property Changed("first_name") End If End Set End Property _ Public Property language() As String Get Return _last_name End Get Set(By Val value As String) If ((_last_name = value) = False) Then **Send Property Changing()** _last_name = value Send Property Changed("last_name") End If End Set End Property _ Public Property email() As String Get Return _email End Get Set(By Val value As String) If ((_email = value) = False) Then **Send Property Changing()** _email = value Send Property Changed("email") End If End Set End Property #End Region #Region "Linq Methods" Public Event Property Changing As Property Changing Event Handler Implements System. Property Changed Event Is Nothing) = False) Then Raise Event Property Changed(Me, New Property Changed Event Args(property Name)) End If End Sub #End Region End Class This is how I'm trying to update a Student Using context As New db Students(str Conn String) Dim tmp Student = (From p In context. The problem is when one of the Properties of the object changed and 'Property Changing' Event is fired using 'Send Property Changing()' method. Students Where p.student_id = Cur Student.student_id Select p). With LINQ, you don't need to do a Where clause or form a list if you are only looking for a UNIQUE/SINGLE/SPECIFIC item. 2) If you wanted to update a property of the Product object, you would typically use a form input, so your next step is to create a View and pass your original model to the View for editing. I get the record using the query: Dim values = From n In entities. Looks like, update Model is working, but since I am not updating anything, there is no change in the DB.Note that since I am using the northwind database in this demo, then deleting of customer data directly will throw an exception because this table is being referenced to other table like Orders .So in order for the code above to work and just for the simplicity of this demo, I remove the relationships to the table that referenced it.
As you can see, the code above is very straight forward and self explanatory.
Since this is a continuation of my previous example so I would suggest you to refer that first before you go any further.
If you look at my previous example you will notice that the html markup above is a bit similar.
What happened there is we created a new instance of the Data Context and then we query the Customer object based on the ID using the LINQ syntax and passed it in a variable customer.
The Single function is an eager function which returns the only element of a sequence that satisfies a specified condition.
In simple terms "It enables the update of data using LINQ queries via WCF Service".