Question

I don’t know what I’ve done wrong, or what could have caused this bug. When I submit this form to the controller, the controller receives 2 empty fields:

Here is the form inside the view:

@Using Html.BeginForm("contactSearch", "search", FormMethod.Post)
    @Html.TextBox("SearchString")
    @Html.DropDownList("opportunite", "Choisissez une opportunité")
    @<input type="submit" value="Submit!" />
End Using

And here is the controller:

    <HttpPost()>
    Function contactSearch(ByVal search As String, ByVal opportunite As opportunite) As ViewResult
        If opportunite Is Nothing Then
            ModelState.AddModelError("opportunite", "Opportunite is empty")
            ViewBag.opportunite = New SelectList(db.opportunite, "idOpportunite", "nomOffre")
            Return View()
        End If
  ...

---

I Still have a little problem, If I write :

 Function contactSearch(ByVal searchString As String, ByVal opportunite As Integer)

And if one of those fields is empty, I got this error : The parameters dictionary contains a null entry for parameter ‘opportunite’…

So, the only way I have to solve this was to use the code below. Isn’t there any better way to solve this?

    Function contactSearch(ByVal search As String, ByVal opportunite As opportunite) As ViewResult
        Dim opport As Integer = 0
        Try
            opport = Val(Request("opportunite"))
        Catch ex As Exception
        End Try

        If opport = 0 Then

Answer 1

You incorrectly named your action arguments. Should be like this:

<HttpPost()>
Function contactSearch(ByVal searchString As String, ByVal opportunite As String) As ViewResult
    ...

Notice that the 2 arguments are of type String. In your code you have used some custom opportunite type for the second argument but this doesn’t make sense because a DropDownList sends only the selected value. You cannot expect it to bind to a complex type.