The #develop teamblog
#  Tuesday, 01 April 2008

Starting with version, the C# code completion in SharpDevelop has support for implicitly typed lambda expressions.

Given a variable "IEnumerable<MyClass> items" and the "Select" extension method from LINQ, typing "items.Select(i => i." now shows the members of MyClass. And if the result of the Select call is assigned to an implicitly typed variable, SharpDevelop is now able to infer that the variable has the type IEnumerable<return type of the lambda expression>.

Unlike all other expressions in C#, the type of a lambda expression cannot be inferred just from by at the expression itself (and the variables used by the expression). To resolve lambda type parameters, we also need to look at the context where the lambda is used. Currently, not all contexts are supported by code-completion, you can find the list of known problems in our bugtracker (Component: DOM / Resolver). Should you find anything where code-completion does not work correctly which is not in that list, please file a bug report in our forum.

The most commonly used context for lambda expressions is method calls, and this is also the most difficult thing to support. It's easy when the method has a clear signature like "void M(Func<int, string> f)", since then SharpDevelop can infer the lambda parameter types directly from the delegate type. But most of the time, things aren't that easy. For example, the signature of the Select method is "IEnumerable<R> Select<T, R>(this IEnumerable<T> input, Func<T, R> f)". Here, SharpDevelop needs to first infer what T is, then it can know what the lambda parameter types are, and only after that it can resolve the lambda expression to infer what R is.

But when the method has multiple overloads, things can get even more messy:
When a method has to overloads "void M(Func<string, int> f)" and "void M(Func<int, int> f)", it is valid to call them like this: "F(i=>i.Length)", "F(i=>i+i)". In the first call, i is a string; in the second, it is int. What SharpDevelop needs to do here is to infer the lambda parameter types for each overload separately, infer the lambda's return type; and then check that against the delegate's signature to see which overload was the correct one.

i=>i.Length is a resolve error if i would be int, but returns the expected int if i is string; so i must resolve to string.
i=>i+i returns a string if i would be string, but returns the expected int if i is int; so i must resolve to int.

Note that because there's no way to tell the type of i before the lambda expression is completed, you cannot expect that SharpDevelop gives you correct code completion for it. "Length" will not be included in the code-completion list for i when you type ".", because at that point, the method call is "F(i=>i)", and i is thus an int. But after the expression is written, SharpDevelop will show a tooltip for "Length", and features like "Go to definiton" and "Find references" will work.

Categories: Daniel
Tuesday, 01 April 2008 08:13:48 (GMT Daylight Time, UTC+01:00)  #    Comments [0]


#  Tuesday, 04 March 2008

In addition to our presence on SourceForge (project page) we now also set up shop at CodePlex (project page). The motivation for this step is to increase awareness about SharpDevelop, and how parts of SharpDevelop can be reused in other applications / scenarios.

Categories: Chris
Tuesday, 04 March 2008 11:42:29 (GMT Standard Time, UTC+00:00)  #    Comments [0]


#  Saturday, 26 January 2008

In SharpDevelop 1.1, the IClass interface had a property that was used in several places in the code:
Once added to a project content, it was immutable. This was not enforced, not even documented. It just happened that no one changed IClass objects except for the code constructing them. After being added to a project content, a class could be removed or replaced by a new version, but if some code still held a reference to an old instance, it could safely access the members without worrying that an update to the class on another thread changed something.

IClass objects are accessed without locks all over the place on the main thread during code completion, and updates on the parser thread should not interfere with that.

However, because I didn't understand this, I broke it in SharpDevelop 2.0. My implementation of partial classes works as following: each file (compilation unit) contributes a part of the class as IClass object representing that part of the class.
Once multiple files register a part of the class in the project content, the project content creates a compound class. This compound class combines the members of all the parts. When updating a part, only the IClass for that part was recreated, and the existing CompoundClass was updated.

The CompoundClass, which could be in use by multiple threads, changed values. To quote Wes Dyer: "Mutation often seems to just cause problems."

Now, that happened to work correctly for quite some time. Most code iterating through a class' members did this with
foreach (IMethod method in c.Methods) {

where c is an IClass (possibly a CompoundClass). An update of the compound class happened to recreate the List<IMethod> behind the c.Methods property, so this code continued to work as expected.

However, in the quick class browser (the two combo boxes above the code window), there was code similar to this:
list.Sort(c.Methods.Count, c.Properties.Count); // sort the properties without mixing them up with the methods

Suddenly, due to the addition of partial classes, this became a race condition waiting to happen. But it was found in time for the SharpDevelop 2.0 release, and I fixed the crash.
But I didn't know much about immutability back then, so what I did was the worst fix possible:
lock (c) { ... }
And in CompoundClass, during update of the parts: lock (this) { ... }

Now, this is not only bad because it's fixing the symptom instead of the problem and it leaves the possibility for similar problems elsewhere in the code - though it might have been the only instance of the problem, since no other crashes due to this have been found while SharpDevelop was using the fix (all 2.x releases use it, including the current stable release, SharpDevelop 2.2.1).

But multi-threading (without immutability) is not hard, it's really, really hard. So it's not really surprising that some day, I found this code to deadlock.

So where's the deadlock?
First I must tell you the other lock we're colliding with: every project content has a lock that it uses to ensure that GetClass() calls are not happening concurrently when the list of classes is updated. So the parser thread acquires the project content lock and then the CompoundClass lock to update the CompoundClass.

But why would the AddRange / Sort code deadlock with this? The comparer used for list.Sort() sorts the members alphabetically using their language-specific conversion to string. In the case of methods, this includes the parameter list, including the parameter types.

What you need to know here is that type references (IReturnType objects) are not immutable - they need to always reference the newest version of the class, as we cannot afford rebuilding all IReturnType objects from all classes in the solution whenever any class changes. Now remember that C# allows code like "using Alias = System.String; class Test { void Method(Alias parameter) {} }".

In this case, the quick class browser correctly resolves the alias and reports "Method(string parameter)". This means that our Sort() call actually sometimes needs to resolve types! And resolving types works using IProjectContent.SearchType, which locks on the project contents' class list lock. And that's our deadlock.

I think it's near impossible to find this kind of deadlock until it occurs and you can see the call stacks of the two blocked threads.
Remember that the actual Method->string conversion and the type resolving is language-specific; it may or may not happen to take a lock for other language binding AddIns.

I fixed the deadlock on trunk (SharpDevelop 3.0) a few months ago by removing the lock on CompoundClass and instead doing this:
int count = list.Count;
list.Sort(count, list.Count - count);

It's still a hack, but this doesn't have any side effects (like taking a lock). And it works correctly under our (new) rule (undocumented rule, aka. assumption) that multiple c.get_Methods calls may return different collections, but the collection's contents don't change.

"foreach (IMethod method in c.Methods) { ... }" is safe, but "for (int i = 0; i < c.Methods.Count; i++) { IMethod method = c.Methods[i]; ... }" can crash.

But that's quite a difficult rule compared to "IClass never changes". So after reading Erip Lippert's series on immutability, I finally decided to make IClass immutable again.

It's "popsicle immutability", that means IClass instances are mutable, but when the Freeze() method is called, they become immutable. And this time, immutability is enforced, trying to change a property of a frozen IClass will cause an exception. Adding an IClass to a project content will cause it to freeze if it isn’t already frozen, so it's guaranteed that IClass objects returned by GetClass or by some type reference are immutable.

Categories: Daniel
Saturday, 26 January 2008 23:30:59 (GMT Standard Time, UTC+00:00)  #    Comments [0]


#  Wednesday, 23 January 2008

A change that happened rather early in the development process of SharpDevelop 3.0 (revision 2658, 8/13/2007) was that we replaced NDoc (a stalled open source project) with Sandcastle Help File Builder (SHFB). SHFB looks and feels similar to NDoc, however, it builds on top of Sandcastle, a documentation generation tool by Microsoft.

Our build server (revision 2913 and higher) contains SHFB, which itself builds on top of the January 2008 release of Sandcastle (both are at the moment the latest releases of their respective projects). SharpDevelop 3.0 setup ships with SHFB, however, Sandcastle itself does not and must be installed separately! (this might change in the future once the final license of Sandcastle is known)

Because of the regular releases of Sandcastle and SHFB, the distribution of SharpDevelop 3.0 might ship with older versions of SHFB than currently available for download. Thanks to Eric Woodruff, the maintainer of SHFB, this is not a big deal - he is offering a download specific for SharpDevelop:

All you have to do is first delete the contents of the following installation directory (including subdirectories):

Then simply unzip the SHFB distribution archive into this folder and presto - you are now using the latest version of SHFB from inside SharpDevelop!

Categories: Chris
Wednesday, 23 January 2008 08:40:44 (GMT Standard Time, UTC+00:00)  #    Comments [0]


#  Tuesday, 15 January 2008

This question came up for example in the thread SharpDev 2.2.x on BuilderServer (this thread was started because we ceased to automatically build v2.2 on 1/11/2008).

The answer is Yes. Development of SharpDevelop 2.2 stopped with revision 2675 (8/28/2007), which is three revisions higher than the officially shipping version of SharpDevelop 2.2 (Download, 8/8/2007). The three non-shipping commits are:

  • 2673: Improved CSharpCodeCompletion sample: add tool tip support, show only one entry for overloaded methods
  • 2674: Fixed some off-by-one bugs in the CSharpCodeCompletion example (caused by the different line counting in the parser and the text editor).
  • 2675: CSharpCodeCompletionSample: show xml documentation

All three were (of course) merged into Montferrer (SharpDevelop 3.0), this merge happened in revision 2679. However, those commits did not merit a release of a new setup because those were all changes to a sample shipping only in the source download.

Since releasing v2.2.1 all work stopped on the 2.x series of SharpDevelop. Our efforts went (and still go) into SharpDevelop 3.

Categories: Chris
Tuesday, 15 January 2008 10:37:39 (GMT Standard Time, UTC+00:00)  #    Comments [0]


#  Friday, 11 January 2008

In continuing to list changes to SharpDevelop 3, we are going to talk about the code coverage addin in SharpDevelop 3 "Montferrer" in this blog post.

Previously, the addin used NCover for calculating code coverage (this is a metric you gain by writing unit tests). However, recently NCover was turned into a commercial product. Because we only include / support tools that are free to use for anyone (commercial or open source / hobby development), we switched to a different tool - PartCover.

This change happened in rev 2744 on 19th of November last year. The addin has retained its original functionality, however, for end users there is an important change: you no longer need to download and install a separate package (as it was the case with NCover), PartCover is part of the SharpDevelop setup. You are good to go right after installation!

Categories: Chris
Friday, 11 January 2008 11:02:23 (GMT Standard Time, UTC+00:00)  #    Comments [0]


#  Thursday, 10 January 2008

An issue that initially came up in 2006 (Unable to compile #develop: access denied) "resurfaced" on our contributors mailing list because one of our developers ran into this very problem that McAfee blocks access to our Main\StartUp folder:

The problem and a workaround is described in McAfee VirusScan and the Startup folder. However, this developer doesn't have the administrative rights to change this setting of McAfee, so he asked whether we are going to rename the folder.

My take on this issue is that this is a bug in McAfee's software, because willy-nilly disabling anything that resides in a random folder called StartUp isn't a security feature.

Categories: Chris
Thursday, 10 January 2008 17:43:52 (GMT Standard Time, UTC+00:00)  #    Comments [0]


#  Wednesday, 02 January 2008

Over the past months we made a couple of feature changes in SharpDevelop 3 (currently alpha status). One major change is that we moved NAnt and Mono support from the binary distribution (aka "setup") to the source code distribution. You can find the addins ready to build in the \samples directory:

What was the reasoning behind this decision? For NAnt, we had taken this decision a long time ago because SharpDevelop itself no longer uses NAnt as the primary build solution, and as such, the addin wasn't actively enhanced and tested. But it still is a great tool as well as a good sample for building addins with SharpDevelop.

The decision to "relegate" Mono from production to sample status has been based on multiple factors. For one, we only support basic compilation for Mono, no debugger nor any kind of visual designers (like GTK#). We got lots of support questions regarding these, and the honest answer had to be "we won't support that, sorry". Then in December Miguel announced that MonoDevelop will come to Windows (MonoDevelop is a fork of SharpDevelop), which meant that an IDE would come to Windows that fully supports all the things in Mono we don't have.

That's why we decided to make Mono an addin for people who know how to deal with source code, all the features are still there. And now that it is separate, it also makes a great sample addin because of the deepness of integration with low-level features of SharpDevelop.

To sum it up - we didn't remove anything, we just trimmed the setup to include features that are targeted at the Microsoft .NET platform.

Categories: Chris
Wednesday, 02 January 2008 08:15:59 (GMT Standard Time, UTC+00:00)  #    Comments [1]


#  Monday, 19 November 2007

Microsoft just released Visual Studio 2008 and the .NET Framework 3.5.

Download .NET Framework 3.5

To develop applications for the .NET Framework 3.5, download SharpDevelop 3.0 from the build server.

Note that SharpDevelop 3.0 are not release quality builds, especially the integrated debugger is very unstable. As currently no one is working on the debugger (hint: you can help!), I disabled it in SharpDevelop so that people trying SharpDevelop 3.0 do not immediately get exceptions when they try run their programs. To re-enable the debugger, open C:\Program Files\SharpDevelop\3.0\AddIns\AddIns\Misc\Debugger\Debugger.AddIn.addin in a text editor and remove the <DisableAddIn .../> node.

Categories: Daniel
Monday, 19 November 2007 21:35:48 (GMT Standard Time, UTC+00:00)  #    Comments [0]


#  Wednesday, 24 October 2007

Daniel is currently working on areas such as project subsystem or code completion (aside from fixing bugs). Therefore, work on the WPF designer is stalled. But Daniel put together a list of tasks (hard, medium & easy) that you could be helping us with. So if you are interested in helping, and want to be part of writing an open source WPF designer, please do get in touch with me at christophw at!

WPF Designer mini tasks

Here are some jobs to do on the WPF Designer broken into small parts.

Apart from this list, there are also big jobs to do: Data Binding support, support using Styles, support defining resources.

Components to be used by multiple designer parts

Create “Choose Class” dialog

The data binding UI will need a dialog that allows choosing a class from the referenced assemblies. This will be implemented in WpfDesigner.AddIn and made available to WpfDesign.Designer through a service. The referenced assemblies should be inspected using ICSharpCode.SharpDevelop.Dom

This will be used by the “Content” property editor and by the data binding UI.

Support ‘Virtual Design Root Element’

This means that instead of displaying the designed component, the designer is able to display another component as if it was the root component. The designer should provide a “Back” button on the design surface to allow the user to go back to the real root component.

This feature is required for designing elements that cannot be designed directly on the main design surface, e.g. Tooltips

Write menu designer

Priority: High

The menu designer might be a dialog box that allows editing the menu in a tree view; or it might be an in-place menu designer like the Windows.Forms designer.

Property editing support

Here I’m listing properties that could need improved editing support.

When implementing property editors, take care that the editor should also work when multiple components with different property values are selected, so you always need a way to represent the ‘ambiguous’ value.

Properties of type Brush (e.g. Control.Background / Control.BorderBrush)

Priority: High

Change ICSharpCode.WpfDesign.Designer.Controls.TypeEditors.BrushEditor to include a little drop down button, the drop down should allow to choose the brush type (SolidColorBrush, etc., we don't need to support all of them at the beginning) and allow the user to edit the brush according to the chosen type.

Properties of type BitmapEffect / BitmapEffectInput (e.g. UIElement.BitmapEffect / UIElement.BitmapEffectInput)

Priority: Low

Implement a TypeEditor (similar to BrushEditor) for the types BitmapEffect and BitmapEffectInput. Could be as simple as a combo box with the most commonly used effects.

Properties of type ICommand (e.g. ButtonBase.Command)

Priority: Medium

There should be a way to choose the command to use from some kind of list.


Priority: High

The “C” button should be made a drop down button (like the one used for the Brush editor), it should present “null”, “string”, and menu items for creating commonly used child configurations (e.g. StackPanel with Image and Text when the parent is a button), and “choose class” to create arbitrary objects. This depends on “Create Choose Class Dialog”.

Properties of type ContextMenu (e.g. FrameworkElement.ContextMenu)

Priority: Medium

Provide a way to create and edit a context menu inside the designer.

Properties of type InputScope

Priority: Low

Research what an InputScope is and if/how we should allow the user to edit it.

Properties of type Transform

Priority: Low

Similar to the BrushEditor, provide a drop down to choose from the different available transforms and allow editing the transform properties.


Priority: Medium (setting string tool tips), Low (designing complex tool tips)

Should be editable similar to ContentControl.Content, but has to allow the user to design complex tooltips. Depends on “Support ‘Virtual Design Root Element’”

Properties of type FontStretch / FontStyle / FontWeight

Priority: Low

Provide a drop down with the available settings

Properties of type FontFamily

Priority: Low

Use a dialog to allow the user to choose the font to use.

Properties of type Nullable<bool> (e.g. ToggleButton.IsChecked)

Priority: Low


Priority: Low

There are two main usage scenarios: this property is specified using data binding (this doesn’t need to be handled by the type editor), or there are some hard coded values.

Write a type editor to support entering string values.


Priority: Low

Label.Target is set to the control described by the label (the control getting focus when Alt+Access Key is pressed). This is done using data binding, but choosing the target from the data binding dialog is too tedious – drag’n’drop of a crosshair on the target control would be much easier. Depends on data binding support.

Properties of type ImageSource (e.g. Image.Source)

Priority: High

Allow choosing a “Resource” element already part of the project, or choose a file and it will get added to the project. This TypeEditor would be implemented in WpfDesign.AddIn and not WpfDesign.Designer because it needs access to the project in SharpDevelop

Properties of type ViewBase (e.g. ListView.View)

Priority: Low

Provide a drop down with the most commonly used views.

Categories: Chris
Wednesday, 24 October 2007 19:01:35 (GMT Daylight Time, UTC+01:00)  #    Comments [0]


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