WPF: slow template instantiation_问答_开发者_运维开发者技术经验分享

I have a WPF application, and it's slow.

It is NOT the rendering. Firstly, the rendering is quite simple, and secondly, I looked at it with WPF Performance Toolkit - nothing.

It is开发者_运维百科 NOT in my own code. Firstly, the unit tests work fast, and secondly, if I replace all DataTemplates with blank ones, everything works fast.

So far, it looks like the slow part is template instantiation. That is, when you start the application, and open some complicated screen, it takes a lot of time. And by "a lot" I mean "a lot". Sometimes can be as much as 3-5 seconds - for example, when there's a datagrid with 100 rows. But when you go to another tab, and then go back to that same screen, it opens fast (as long as its viewmodel stays put).

This is very annoying not just because it's slow, but because I can't do anything about it. If I had some control over the slowness, I could, maybe, display some "opening, please wait" message or something...

Besides, when I look at some other WPF applications (most notably, ILSpy), they seem to work reasonably fast, despite the large amounts of data. This makes me believe that I'm probably doing something wrong. But I have no idea where to start.

Any ideas? Any classic mistakes? Any tips?

My exerience comes from working on the WPF mind mapping application NovaMind

A couple of months ago we completely rewrote our intermediate layer to solve the performance issues we had experienced. In a nutshell, creating our user controls seemed to be way to slow. Unfortunately I couldn't find a great way to profile the performance as neither the WPF Performance Suite nor commercial applications such as ANTS Profiler give you any detailed information on this part of the WPF process. (I asked this question back then)

We resorted to manually test our application by trial and error and removed parts of our user controls to see what exactly is the culprit.

In the end we solved the performance issues by completely rewriting our controls. We also cut down on the complexity of our visual tree dramatically. Before the rewrite, one of our most used user controls, when inspected with Snoop, consisted out of 61 different things, now there are only 3. Wherever possible we only added things to the visual tree on demand. (As you know in XAML even when you set things to Collapsed, they need to be created first). Finally we were forced to write our own rich text rendering control as the built in RichtextBox is ridiculously slow and the visual tree of the RichtextBox is quite complex.

I don't know if this will apply to your situation but I would recommend that you investigate your user controls and see if they are complex. Maybe you have things that you could trim. Low hanging fruits would be parts that are only rarely visible or can be created in a lazy manner. You could create these parts from code behind when necessary rather than having them in XAML. This should help you a lot.

Otherwise virtualization is your friend, if possible. In our case we couldn't do that unfortunately.

This sounds similar to a problem i was having. I posted the fix here: WPF UI Automation issue . Just posting for the benefit of searchers, as it took ages to resolve.

Following comment on link only answer, here is the crux of that post:

I did the following:

Downloaded Hotfix - - http://archive.msdn.microsoft.com/KB978520 (may not be required)
Downloaded Hotfix - - http://archive.msdn.microsoft.com/KB2484841 (definitely required even if you have Windows 7 / .NET 4)
Improved the code further (the validation was causing an excess of objects) - Why does WPF Style to show validation errors in ToolTip work for a TextBox but fails for a ComboBox?

It may be that only Number 3 was required, but it worked. Just posting here so people dont lose the days I lost in memory profilers etc.

User Control in your data template, is not completely bad idea but if you crave for performance then you should consider switching to lighter control. For example, having a UserControl just hosting a TextBox is very bad idea, as UserControl is made up of ContentControl, ContentControl hosts ContentPresenter and ContentPresenter will host TextBox so if you notice your Visual Tree, it has three new layer of UI Elements. Reducing Visual Tree will certainly improve the performance.

Most likely, I would suggest creating Custom Controls that may be a completely a new control having few dependency properties that can relate to data you want to present and you can have its own custom template in generic.xaml. Second, you can just simply derive a control from existing controls and redefine its default template in generic.xaml.

This approach will certainly work better as you will be reducing your Visual Tree, thus reducing Visual State Manager's job.

Changing theme or template will be slower then changing the element that hosts content. And let the element have the default template in its own generic resource dictionary.

Try moving all the resources up as far as they'll go, preferably into app.xaml
Check if you could use StaticResource instead of dynamic ones, static ones are alot faster
If possible, try using depedency properties in your VMs, especially if you have alot of them at once or if they have alot of properties. That will keep wpf from having to do a bunch of reflection.

You mention you are using a DataGrid with, say, 100 rows. A likely culprit of your perf problems is that whatever datagrid you are using isn't doing virtualization, and so your visual tree is gigantic.

Normally, long startup time in WPF screens points to a large visual tree.

I'm not sure if you're using a datatemplate per row, or some 3rd party grid that binds columns, or what - but lets say you have 8 columns with controls. Depending on your grid/validation/etc, this could be a visual tree of 20-60 items per row. If you have a combobox, then each item in the dropdown may be created per row as well.

To fix this just takes watching the details, and taking measures as you go:

Use a virtualizing control as much as possible. This means using a virtualizingstackpanel inside list controls, and making sure your 3rd party controls do as well (many stock WPF controls do now by default)
Do not overuse UserControls, composite controls, etc. Adding depth adds time, and putting in extra visual tree depth in a datatemplate or other repeated area adds up fast.
If all else fails, show a simple screen and add controls through code to improve perceived performance