Unable to generate code for a value of type...

[Chris Bower]

Reposted from aspnet.buildingcontrols:
Ok, I've got a bunch of derived controls that all have a property Rights of
type Rights (Rights is an Enumerator). I wrote a custom TypeConverter so
that I can use comma separated values in design-time. The TypeConverter
works great in design-time. It converts to and from just fine... However,
when I try to load any page in the site now I get the following error
(Following the error is code for the TypeConverter:

Exception Details: System.Web.HttpException: Unable to generate code for a
value of type 'Intranet.CustomControls.Rights'. This error occurred while
trying to generate the property value for Rights.

Stack Trace:

[HttpException (0x80004005): Unable to generate code for a value of type
'Intranet.CustomControls.Rights'. This error occurred while trying to
generate the property value for Rights.]

System.Web.Compilation.CodeDomUtility.GenerateExpressionForValue(PropertyInf
o propertyInfo, Object value, Type valueType) +2253

System.Web.Compilation.TemplateControlCompiler.BuildBuildMethod(ControlBuild
er builder, Boolean fTemplate, PropertySetterEntry pse) +2538

System.Web.Compilation.TemplateControlCompiler.BuildSourceDataTreeFromBuilde
r(ControlBuilder builder, Boolean fInTemplate, PropertySetterEntry pse) +794

System.Web.Compilation.TemplateControlCompiler.BuildSourceDataTreeFromBuilde
r(ControlBuilder builder, Boolean fInTemplate, PropertySetterEntry pse) +352

System.Web.Compilation.TemplateControlCompiler.BuildSourceDataTreeFromBuilde
r(ControlBuilder builder, Boolean fInTemplate, PropertySetterEntry pse) +352
System.Web.Compilation.TemplateControlCompiler.BuildMiscClassMembers()
+51
System.Web.Compilation.PageCompiler.BuildMiscClassMembers() +10
System.Web.Compilation.BaseCompiler.BuildSourceDataTree() +1276
System.Web.Compilation.BaseCompiler.GetCompiledType() +129
System.Web.UI.PageParser.CompileIntoType() +59
System.Web.UI.TemplateParser.GetParserCacheItemThroughCompilation() +126



Following is the code for my TypeConverter:

Public Class RightsConverter
Inherits TypeConverter


Public Overloads Overrides Function ConvertFrom(ByVal context As
System.ComponentModel.ITypeDescriptorContext, ByVal culture As
System.Globalization.CultureInfo, ByVal value As Object) As Object
If IsNothing(value) Then
Return 0
End If
Dim x As String
If value.GetType Is GetType(String) Then
Dim data As String = CStr(value)
Dim r As Rights
r = CType([Enum].Parse(GetType(Rights), data), Rights)
Return r
End If
End Function

Public Overloads Overrides Function ConvertTo(ByVal context As
System.ComponentModel.ITypeDescriptorContext, ByVal culture As
System.Globalization.CultureInfo, ByVal value As Object, ByVal
destinationType As System.Type) As Object
If Not IsNothing(value) Then
If Not value.GetType Is GetType(Rights) Then
Throw New ArgumentException("Invalid Rights Enum", "value")
End If
End If
If destinationType Is GetType(String) Then
If IsNothing(value) Then
Return String.Empty
End If

Dim r As Rights = CType(value, Rights)
Dim rVal As String
Dim sa() As String
Dim name As String
Dim i As Integer
For Each name In [Enum].GetNames(GetType(Rights))
i = [Enum].Parse(GetType(Rights), name)
If (i And r) > 0 Then
If IsNothing(sa) Then
ReDim sa(0)
sa(0) = name
Else
ReDim Preserve sa(sa.Length)
sa(sa.GetUpperBound(0)) = name
End If
End If
Next
If Not IsNothing(sa) Then
For i = 0 To sa.GetUpperBound(0)
If i > 0 Then
rVal &= ", " & sa(i)
Else
rVal = sa(i)
End If
Next
Return rVal
Else
Return ""
End If
End If
End Function

Public Overloads Overrides Function CanConvertFrom(ByVal context As
System.ComponentModel.ITypeDescriptorContext, ByVal sourceType As
System.Type) As Boolean
If sourceType Is GetType(String) Then
Return True
ElseIf sourceType Is GetType(Integer) Then
Return True
Else
MyBase.CanConvertFrom(context, sourceType)
End If
End Function

Public Overloads Overrides Function CanConvertTo(ByVal context As
System.ComponentModel.ITypeDescriptorContext, ByVal destinationType As
System.Type) As Boolean
If destinationType Is GetType(String) Then
Return True
ElseIf destinationType Is GetType(Integer) Then
Return True
Else
MyBase.CanConvertFrom(context, destinationType)
End If
End Function
End Class


Here is what the property looks like on the controls:

<Description("The rights required to view this control."), _
Editor(GetType(RightsEditor), GetType(UITypeEditor)),
DefaultValue("Everyone")> _
Public Property Rights() As Rights
Get
Return _rights
End Get
Set(ByVal Value As Rights)
_rights = Value
End Set
End Property

Anyone have any ideas as to what could be wrong?

 

[Chris Bower]

As an update:
I changed the CanConvertTo so that it will return True for an
InstanceDescriptor and then messed around with some code to create an
InstanceDescriptor in the ConvertTo function:

If destinationType Is GetType(InstanceDescriptor) Then
Dim mi As MethodInfo = GetType([Enum]).GetMethod("Parse", New
Type() {GetType(Type), GetType(String)})

Dim r As Rights = CType(value, Rights)
Dim id As New InstanceDescriptor(mi, New Object()
{GetType(Rights), r.ToString})
Return id
End If

Now when I load the page I get an Object reference not set to an instance of
an object error. I know for sure that the InstanceDescriptor can be used to
create an instance of the Rights enum, as I tested it by using Invoke so I'm
confused as to why this doesn't work.

I also realize that using an InstanceDescriptor isn't the way I should
really be going since this is an enum and doesn't have a parameterized
constructor or anything, but I can't think of anything else. Any thoughts?

 

[MSFT]

Hi Chris,

I got same error when I tested your code. Anyway, the problem disappeared
after I change your property name:

<Description("The rights required to view this control."), _
Editor(GetType(RightsEditor), GetType(UITypeEditor)),
DefaultValue("Everyone")> _
Public Property MyRights() As Rights
Get
Return _rights
End Get
Set(ByVal Value As Rights)
_rights = Value
End Set
End Property

I may test this in your actual code to see if it will work.

Luke
Microsoft Online Support

Get Secure! www.microsoft.com/security
(This posting is provided "AS IS", with no warranties, and confers no
rights.)

 

[Chris Bower]

Hmm.. I tried that with one of my controls but the only thing that changed
was the error message:
Unable to generate code for a value of type
'Intranet.CustomControls.Rights'. This error occurred while trying to
generate the property value for DisplayRights.

I take it you're looking at the sample I put together for Michael? Has this
worked with that sample?

 

[Chris Bower]

For posterity's sake:
This turned out to be a bug in the 1.1 framework. There a KB article about
it here: http://support.microsoft.com/default.aspx?scid=kb;en-us;825082