Category: NETCF

Using these techniques it’s possible to extend existing controls and add attributes to improve their designer experience. To illustrate this I’ve taken the example of the ComboBoxEx control. This extends the ComboBox control by overriding runtime behaviour to overcome a data binding issue, and adds BeginUpdate and EndUpdate methods to improve performance when filling the list of items.

The designer experience for the control inherits the behaviour of the ComboBox control. Since the ComboBox’s own designer excludes some designer support which the control now implements as of Service Pack 2 such as Fore and Back Colors we can add these to our designer and have the designer insert the code to set the colour. The following block of code implements these properties in the design version of the control:-

#if DESIGN


[Browsable(true),

EditorBrowsable(EditorBrowsableState.Always),

DesignerSerializationVisibility(DesignerSerializationVisibility.Visible)]

public new System.Drawing.Color ForeColor

{

get

{

return base.ForeColor;

}

set

{

base.ForeColor = value;

}

}


[Browsable(true),

DesignerSerializationVisibility(DesignerSerializationVisibility.Visible)]

public new System.Drawing.Color BackColor

{

get

{

return base.BackColor;

}

set

{

base.BackColor = value;

}

}

#endif

Once built we have a combobox with color support, and because the forms designer in Visual Studio uses a standard ComboBox for drawing it already supports drawing itself with the specified colour.

 

Part 1 | Part 2 | Part 3 | Part 4

How the designer interprets your components is from a mixture of reflection to actually see what properties you expose, but also attributes which allow you to override this behaviour.

The first attributes which are required for any component to appear in the toolbox are:-

#if DESIGN

[ToolboxItemFilter(“NETCF”,ToolboxItemFilterType.Require),

ToolboxItemFilter(“System.CF.Windows.Forms”, ToolboxItemFilterType.Custom)]

#endif

This ensures that the component only appears on the device controls toolbar and not within a desktop project. We wrap this in an if DESIGN block so that the attribute is not added to the runtime control (because the CF assemblies don’t include this attribute). The ToolboxItemFilterAttribute can be found in the System.ComponentModel namespace.

If you build the libraries now you should be able to add these components to your toolbox. Open a new device project and open a form in the designer, right click the toolbox and select “Add/Remove Items…” then browse to the output of your project e.g. binDesigner once you have added the file and closed the dialog you should have some new entries in your toolbox:-

In order for the properties pane to work correctly we need to do some further decorating. For most properties you’ll be dealing with fundamental types which visual studio can display automatically. It is a good practise to specify the default values for these fields, in this way if you set the properties to the default it won’t generate code to assign to the property, also the property pane displays non-default values in bold so you can quickly see which have been set to a specific value. The DefaultValueAttribute accepts an object, for example in the case of the ProcessStartInfo the FileName default is an empty string

#if DESIGN
        [DefaultValue(“”), RecommendedAsConfigurable(true)]
#endif
        public string FileName

Some properties will have no meaning at design time such as the Handle property of the Process, using the BrowsableAttribute with a value of false will hide the property

#if DESIGN

[Browsable(false), DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]

#endif

public IntPtr Handle

The DesignerSerializationVisibility attribute ensures that this property is excluded from the data serialized to describe your component.

If you have a property which is of type Object then the designer will have no idea what is valid to assign to this and it will appear greyed out. Some of our components and controls now include a Tag property which allows you to tag an object of any type which may contain supporting data. On the desktop this is exposed as a string, so we do the same in our designer support. At runtime you can still assign any object to this property. We also apply the BindableAttribute which tells the designer that this property may be used in data binding.

#if DESIGN

[Bindable(true), DefaultValue((string) null), TypeConverter(typeof(StringConverter))]

#endif

public object Tag
 

Some properties will use other classes which themselves contain multiple properties. A good example is the ProcessStartInfo which is used with the Process class. In order to allow the designer to display this correctly as a nested object we apply the TypeConverterAttribute and give it a value of ExpandableObjectConverter, this allows the designer to populate the property pane with the various properties contained within it.

#if DESIGN

[TypeConverter(typeof(ExpandableObjectConverter))]

#endif

public sealed class ProcessStartInfo

We apply the same selection of properties to define the default values for the properties within this class. Now the property pane takes on a logical nested appearance and we can setup all of these properties at design time:-

To ensure these properties are written out in our code by the designer we need to add the DesignerSerializationVisibilityAttribute:-

#if DESIGN

[DesignerSerializationVisibility(DesignerSerializationVisibility.Content)]

#endif

public ProcessStartInfo StartInfo

Optionally you can specify categories and descriptions for properties and events. Depending on the user’s preferences the property pane may be shown by category or alphabetically. By default properties are added to the “Misc” category. The grey box below the actual property list will show a short description as defined by the DescriptionAttribute as used here in the BackgroundWorker class.

#if DESIGN

[Category(“Asynchronous”),

Description(“Event handler to run on a different thread when the operation begins.”)]

#endif

public event DoWorkEventHandler DoWork;

Part 1 | Part 2 | Part 3 | Part 4

Introduction

When developing desktop .NET forms projects the toolbox contains a number of components you can drag across to your form and setup via the designer. A component in this case is any class which inherits from System.ComponentModel.Component. Visual Studio generates the appropriate code for you, in just the same way as forms controls except your components sit in a tray below your form.

Over the past few versions of the SDF we have steadily built up a number of components which directly match those available on the desktop, so I decided it would be great to offer exactly the same designer experience.

There are two key points to design time controls, firstly they are compiled against the full .NET framework (since that is what Visual Studio’s form designer uses), secondly they include a number of special attributes to setup the correct behaviour of the component and the properties window.

Setting Up the Build Process

There are two ways to build your designer assembly, either via the command line usually by building a batch file to call the C# compiler with your code files (That’s correct no VB.NET design time controls at this stage) this article was probably the first to describe this process and is still just as relevant today. The other way is to create a desktop Class Library project type and insert your existing code files.

This is the approach I took this time as I’ve used command line build before and fancied a change. I started with a Solution which contains all the affected SDF assemblies – OpenNETCF, OpenNETCF.Drawing, OpenNETCF.Windows.Forms and OpenNETCF.WindowsCE.Forms. OpenNETCF.Drawing exposes no designable types but is used by the two forms assemblies. Within this solution file I created 5 new desktop Class Library projects – OpenNETCF.CF, OpenNETCF.CF.Drawing, OpenNETCF.CF.Windows.Forms and OpenNETCF.CF.WindowsCE.Forms, I then removed these new projects from the solution and moved the project files (.csproj) into the respective folder with their device equivalent (note that device projects have the .csdproj extension). I then opened each of the runtime projects in a text editor and copied all the entries into the design time projects. Finally back in Visual Studio I add these new desktop projects into the same solution. Next in order to allow both sets of files to build side-by-side I create a new configuration for the project called “Designer”. Then in my default “Debug” configuration for the entire solution I set the design time projects (OpenNETCF.CF.*) to use the Designer configuration and all the runtime projects to use the Debug configuration.

Next I go into the project properties for each of the design time libraries and set the output folder to binDesigner and set a conditional compilation constant for “DESIGN”. We have already used this constant for previous versions when adding designer support to the controls so this already makes much of the libraries “designer safe”.

These OpenNETCF libraries include dependencies to each other so OpenNETCF.CF.Drawing requires a reference to OpenNETCF.CF, OpenNETCF.CF.Windows.Forms requires a reference to both these and so on. These references are easily added with the Add Reference dialog and switching to the Projects pane. Next each of the design time projects needs a couple of standard references to the .NETCF designer assemblies:-

• System.CF.Design
  
• System.CF.Drawing
  
• System.CF.Windows.Forms

Additionally a reference to Microsoft.CF.WindowsCE.Forms was required in OpenNETCF.CF.WindowsCE.Forms since InputPanelEx derives from InputPanel. All of these designer assemblies is found within the Visual Studio installation e.g.

C:Program FilesMicrosoft Visual Studio .NET 2003CompactFrameworkSDKv1.0.5000Windows CEDesigner

The advantage of going through all these hoops is that both the design time and runtime projects point to exactly the same source code and you can build both assemblies from within your visual studio solution.

 

Designer Support

For each component or control which is exposed to the toolbox an image is required. This should be a 16×16 bitmap with the name of the control including full namespace e.g.

OpenNETCF.Diagnostics.Process.bmp

This is added to the design time project as an Embedded Resource in the root of the project (otherwise folder names are added to the resource name). We could try building the solution now, and will probably come across errors.

A quick way to simplify the process is to remove any code files which are not required by any of your designable components, alternatively you could exclude entire files or code blocks from the design time build process by encapsulating them in if blocks using the compilation constant we setup e.g.

#if !DESIGN

public class NativeStuffWeDontNeedAtDesignTime

{

}

#endif

Concentrating on our components you can actually be quite ruthless with this conditional compilation as long as you expose the public properties which will be displayed in the properties window in the designer. Once you have successfully built the whole solution you’ll have a full set of runtime and design time assemblies, however they are not ready just yet as with all new builds they need decorating before we can move in…

Part 1 | Part 2 | Part 3 | Part 4

This VB.NET code will work on Smartphone and Pocket PC Phone devices and return details of the current GSM operator (though it probably works on CDMA also). It relies on Alex Feinman’s excellent TAPI wrapper whish you can download here. Using the library we create a line object which we pass the handle of (line.hline) into lineGetCurrentOperator, one of the ExTAPI functions. For simplicity the structure is just passed as one big byte array then the strings are copied out from it and have trailing nulls chopped off.

‘gets the textual representation of the operator
Public Function GetCurrentOperator(ByVal line As OpenNETCF.TAPI.Line) As Operator
Dim result As Integer
Dim nullindex As Integer

‘stores operator details
Dim lo As New Operator

Dim buff(140) As Byte

‘copy LINEOPERATOR_USEFIRSTAVAILABLEINDEX to struct
BitConverter.GetBytes(-1).CopyTo(buff, 0)

‘call tapi method
result = lineGetCurrentOperator(line.hLine, buff)

If result < 0 Then
‘error encountered
Throw New System.Runtime.InteropServices.ExternalException(“TAPI Error getting operator: “ + result.ToString())
End If

‘index
lo.Index = BitConverter.ToInt32(buff, 0)
‘get status
lo.Status = BitConverter.ToInt32(buff, 4)
‘get valid fields
lo.ValidFields = CType(BitConverter.ToInt32(buff, 8), OperatorFormat)



‘long name
If (lo.ValidFields And OperatorFormat.AlphaLong) = OperatorFormat.AlphaLong Then
lo.LongName = System.Text.Encoding.Unicode.GetString(buff, 12, 64)
nullindex = lo.LongName.IndexOf(Chr(0))
If nullindex > -1 Then
lo.LongName = lo.LongName.Substring(0, nullindex)
End If
End If


‘copy short name
If (lo.ValidFields And OperatorFormat.AlphaShort) = OperatorFormat.AlphaShort Then
lo.ShortName = System.Text.Encoding.Unicode.GetString(buff, 76, 32)
nullindex = lo.ShortName.IndexOf(Chr(0))
If nullindex > -1 Then
lo.ShortName = lo.ShortName.Substring(0, nullindex)
End If
End If

‘copy num name
If (lo.ValidFields And OperatorFormat.Numeric) = OperatorFormat.Numeric Then
lo.NumName = System.Text.Encoding.Unicode.GetString(buff, 108, 32)
nullindex = lo.NumName.IndexOf(Chr(0))
If nullindex > -1 Then
lo.NumName = lo.NumName.Substring(0, nullindex)
End If
End If

Return lo

End Function

Declare Function lineGetCurrentOperator Lib “cellcore.dll” (ByVal hLine As IntPtr, ByVal operator As Byte()) As Integer

Public Class Operator

   Public Index As Integer
   Public ValidFields As OperatorFormat
   Public Status As Integer
   Public LongName As String
   Public ShortName As String
   Public NumName As String

End Class

_
Public Enum OperatorFormat
   None = &H0
   AlphaShort = &H1
   AlphaLong = &H2
   Numeric = &H4
End Enum

 

To follow up from a recent enquiry on the newsgroup, neither .NETCF v1.0 or v2.0 include the FolderBrowserDialog component. The main reason for this is that this functionality is not implemented in all flavours of Windows CE, for example Windows Mobile (Pocket PC / Smartphone) doesn’t include support for this dialog. If your device does support this shell feature then here is a simple wrapper I wrote which wraps the SHBrowseForFolder API in a FolderBrowserDialog class, which mimics the desktop equivelent. The code is packaged with a quick three line demonstration using the dialog. This works on the CE.NET 4.1 Emulator shipped with Visual Studio 2003.

Download InTheHand.Windows.Forms.FolderBrowserDialog.zip

If your platform is unsupported the control will throw a PlatformNotSupportedException when you call ShowDialog(). If you want to create this kind of functionality on Windows Mobile then a good starting point is the code accompanying this article at MSDN.

Announced on Jono’s blog the Patterns & Practices team are looking at what guidance they can provide for device development. They have now setup a formal online survey to capture your wishes and needs, so I recommend you stop by and add your thoughts:-

Fill in the survey

Personally I’d like to see some kind of Power Management application block and accompanying guidelines produced, along with the obvious choice of a port of the Smart Client Offline block.