xmlns question - WPF Discussion Boards

How to remember the position of a GridSplitter

19-Jun-09 11:37

Glad to help.

Christian Graus

Driven to the arms of OSX by Vista.

"! i don't exactly like or do programming and it only gives me a headache." - spotted in VB forums.

I can do things with my brain that I can't even google. I can flex the front part of my brain instantly anytime I want. It can be exhausting and it even causes me vision problems for some reason. - CaptainSeeSharp

Re: Canvas with an Image

Mark Salsbery21-Jun-09 7:33

Mark Salsbery

21-Jun-09 7:33

This shouldn't be a "bumpy ride" if you understand how WPF layout works.

"There is a difference between the properties of Height and Width and
ActualHeight and ActualWidth. For example, the ActualHeight property is
a calculated value based on other height inputs and the layout system.
The value is set by the layout system itself, based on an actual rendering
pass, and may therefore lag slightly behind the set value of properties
such as Height that are the basis of the input change.

Because ActualHeight is a calculated value, you should be aware that
there could be multiple or incremental reported changes to it as a result
of various operations by the layout system. The layout system may be
calculating required measure space for child elements, constraints by
the parent element, and so on."

WPF: The Layout System[^]

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

fjparisIII19-Jun-09 8:57

fjparisIII

19-Jun-09 8:57

The goal is to remember the position of a GridSplitter from one execution of a window to the next so I can restore the previous position when the window reloads.

For purposes of discussion, assume my GridSplitter is vertical. I remember reading somewhere that to remember the position of the GridSplitter all you have to do is remember the width of the left element and when the window loads, set the element to that width.

However, my SizeChanged event for the left element only happens when the window is first loaded. Dragging the position of the splitter (hence changing the size of the left element - as well as the right element) does not generate any more SizeChanged events for the left element. That seems totally illogical.

Here is something else that seems totally illogical. I also tried getting MouseUp and MouseLeftButtonUp events for both the splitter and the Grid element the splitter is in, and I don't get any of these events either!

What could possibly be going on? The element that is in the left column of the Grid is a TreeView and I haven't even started populating it yet.

Re: How to remember the position of a GridSplitter (I "SOLVED" IT MYSELF)

fjparisIII19-Jun-09 11:37

fjparisIII

19-Jun-09 11:37

I searched the Code Project for the answer to this question and couldn't find one. I also Googled for it and found several proposed and confusing answers that I couldn't make much sense of. People don't seem to be very clear about what they really want. So I thought I'd ask the question on this Code Project WPF forum, but in the meantime I kept working on an answer myself. After trying a bunch of possibilities for a couple hours, I got the idea of remembering the width of the ColumnDefinition rather than the width of the element contained in the column. By itself, the latter doesn't work, but it does in conjunection with the former, depending on what you actually want to do. After receiving some success using the column definition, I ran into other problems, stemming from the fuzzy idea I had about the actual behavior I wanted. Eventually I defined that as follows, which may not be what you want:

Before my change, the position of my GridSplitter was automatically set to 1/3 the width of the grid and changing the width of the containing window maintained this 1/3 proportional ratio. I decided that for my application, this was undesirable behavior. I wanted the width of the left panel to remain fixed as the width of the window changed, and I wanted only the width of the right panel to change as I manually changed the width of the window. This required defining my grid columns as follows:

<Grid.ColumnDefinitions>
    <ColumnDefinition Name="treeColumn" Width="0"/>
    <ColumnDefinition Width="Auto" />
    <ColumnDefinition  Width="*"/>
</Grid.ColumnDefinitions>

The middle column corresponds to the GridSplitter. The width of the left column is set to 0 in this markup because that is actually the property I want to set programmatically in code-behind, both when the window is loaded and when the user drags the GridSplitter.

The only thing I had to work out is that the Width property of a ColumnDefinition is a GridLength object, not a simple double.

The other thing I had to figure out is what event to look for. I already explained in my initial post that SizeChanged on the element in the left column didn't work, and neither did MouseLeftButtonUp. I wasn't getting either event. That's because these are bubbling events that are being handled by higher level controls. I needed a tunneling event, a Preview event. For my purposes, PreviewMouseLeftButtonUp on the GridSplitter did the trick. Here is that event from my code-behind:

private void mainSplitter_PreviewMouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
    State.TreeWidth = treeColumn.Width.Value;
    treeCtrl.Width = frameForPages.Width - 16;
}

(The hard-coded 16 is a kludge: the hard-coded width of the left and right border. I'll clean this up later.) Now all I needed was the code to set the initial width of left column (treeControl) when my application started:

treeColumn.Width = new GridLength(State.TreeWidth);
treeCtrl.Width = frameForPages.Width - 16;

So now I know how to save the position of the GridSplitter from one invocation of its window to the next, and the next time someone searches for the answer to this question, hopefully he'll run into this post and see what some of the issues are that need to be addressed to accomplish the behavior he wants.

modified on Friday, October 30, 2009 12:12 PM

Re: How to remember the position of a GridSplitter (I SOLVED IT MYSELF)

Christian Graus19-Jun-09 12:46

Re: How to remember the position of a GridSplitter (I "SOLVED" IT MYSELF)

19-Jun-09 12:46

fjparisIII wrote:
Either I'm trying to do things that nobody knows the answer to or my questions are so stupid that people just laugh when they see them.

The traffic in this forum is pretty slow. However, there's a few people who are very good at WPF, and then there's me, who is doing his best. We'd all answer you, given a chance. Timezones mean you may need to wait a day.

You should use ActualWidth if it exists, rather than width. The preview events always fire, but the non preview events may not fire if something further up the tree consumes the event. Upshot is, I typically use the preview events only.

fjparisIII19-Jun-09 13:55

fjparisIII

19-Jun-09 13:55

Christian Graus wrote:
You should use ActualWidth if it exists, rather than width.

ColumnDefinition.Width is not the same as UIElement.Width. The latter is a double, the former is a GridLength and doesn't work the same way as a UIElement.Width. You can't use ActualWidth to solve this problem.

Christian Graus wrote:
The preview events always fire, but the non preview events may not fire if something further up the tree consumes the event. Upshot is, I typically use the preview events only.

As I explained above, this is because a tunneling event is needed here, i.e. a Preview event.

Re: How to remember the position of a GridSplitter (I SOLVED IT MYSELF)

Christian Graus19-Jun-09 17:37

Re: xmlns question [modified]

19-Jun-09 17:37

fjparisIII wrote:
BTW, I never did get my answer on how to save a lossless rotation of a JPEG. This may be impossible with WPF (you probably could do it in that nightmarish WIC). Looks like I'm going to have to stoop to using the GDI+ .NET classes.

Well, if you read my blog, http://thingsihateaboutmicrosoft.blogspot.com/2009/06/wpf-destroys-images-when-resizing-them.html[^], I started my blog b/c you reminded me of that WPF resizing image bug. If they can't fix that, they are not going to add the sort of thing you wanted to do....

xmlns question

#realJSOP19-Jun-09 4:39

#realJSOP

19-Jun-09 4:39

If I define a namespace (xmlns) in app.xaml, does the whole application assembly see it, or do I have to redefine it in each xaml file from which I wish to use it?

"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001

Eslam Afifi19-Jun-09 6:29

Eslam Afifi

19-Jun-09 6:29

No. An XML namespaces binding scope is limited to the tag where they were defined[^]. I don't know whether XAML is XML v1.0 or v1.1 but a namespace binding attribute value cannot be empty.
And the first binding up the tree from where you use it is the one applied.

<StackPanel>
    <Grid xmlns:sys="clr-namespace:System;assembly=mscorlib">
        <Grid.Resources>
            <sys:Int32 x:Key="i">
                6
            </sys:Int32>
        </Grid.Resources>
    </Grid> <!-- mscorelib binding scope ends here -->

    <Grid xmlns:sys="clr-namespace:System;assembly=System">
        <Grid.Resources>
            <sys:Uri x:Key="uri">
                http://www.codeproject.com
            </sys:Uri>
        </Grid.Resources>

        <Grid xmlns:sys="clr-namespace:System;assembly=mscorlib">
            <Grid.Resources>
                <sys:Byte x:Key="b"> <!-- The binding used is mscorlib's -->
                    8
                </sys:Byte>
            </Grid.Resources>
        </Grid>
    </Grid>
</StackPanel>

There seems to be a problem displaying the code. Solved, the encode HTML option was disabled D'Oh! | :doh:

Eslam Afifi

modified on Friday, June 19, 2009 12:50 PM

Christian Graus19-Jun-09 11:45

19-Jun-09 11:45

That would make sense, right ? I'd also like to be able to define resources in one place and have them included through the project.

#realJSOP19-Jun-09 15:15

#realJSOP

19-Jun-09 15:15

Now you're just talking crazy...

Mark Salsbery21-Jun-09 7:47

Mark Salsbery

21-Jun-09 7:47

Christian Graus wrote:
That would make sense, right ?

No. You don't define namespaces in XAML.

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Web browser application having database

SteveTheThread22-Jun-09 0:18

SteveTheThread

22-Jun-09 0:18

I am right in thinking you are refering to defining a namespace for e.g. a bunch of controls, and you wish to reference those controls in xaml using a (Xml) namespace rather than by code namespace and assembly, as in the example below (controls vs scm)

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:scm="clr-namespace:System.ComponentModel;assembly=WindowsBase"
    xmlns:controls="http://schemas.xxx.com/wpf/xaml/controls">

To create your own (xml) namespace defintion, just done something like the following in you AssemblyInfo file

[assembly: XmlnsDefinition("http://schemas.xxx.com/wpf/xaml/controls", "xxx.Common.Controls")]
[assembly: XmlnsPrefix("http://schemas.xxx.com/wpf/xaml/controls", "controls")]

You can then use the xmlns definition in any xaml files that reference your controls project, but unfortunately, you can not use the xmlns defintition withn the project, eg. in a Resource dictionary within the project, which is understandable, but disappointing.

Rits11038918-Jun-09 21:34

18-Jun-09 21:34

I have to write an web browser application in WPF having database. I want to know if there are good sample database applications. I am looking for something like the sample on Microsoft SQL. I need all the basic functionality expected on line of business applications like master/detail or at least a similar functionality. Someone could please help me!

Christian Graus18-Jun-09 23:54

18-Jun-09 23:54

A SQL database isn't implimented any differently in WPF, compared to a winforms app. I need to know tho, why does your 'web browser application' need a database ?

#realJSOP19-Jun-09 0:11

#realJSOP

19-Jun-09 0:11

Christian Graus wrote:
I need to know tho, why does your 'web browser application' need a database ?

So he can properly catalog his inabilities.

Rits11038919-Jun-09 0:27

19-Jun-09 0:27

i need database because i want to store data from user and show the data to the user on demand Poke tongue | ;-P

Christian Graus19-Jun-09 11:00

19-Jun-09 11:00

What data ? Why ?

Rits11038919-Jun-09 0:24

19-Jun-09 0:24

I have problem that the database created in WPF web browser application cant open.It provides an error.
The following code is written in the page2.xaml.vb under the event button1_click of button1

imports system.data
imports syste.data.sqlclient

dim sqlconnection1 as new sqlconnection(my.settings.database1connectionstring)
dim dr as sqldatareader
dim sqlcommand1 as sqlcommand

try
sqlconnection1.open()
sqlcommand1=new sqlcommand("select FirstName from Table1",sqlconnection1)
dr=sqlcommand1.executereader()
while dr.read()
combobox1.items.add(dr(0))
end while
dr.close()
catch ex as exception
msgbox ex.message
end try
sqlconnection1.close()

THE ABOVE CODE GENRATE THE FOLLOWING ERROR AT RUNTIME
REQUEST FOR THE PERMISSION OF TYPE 'system.sqlclient.sqlclientpermission,system.data,version=2.0.0.0,culture=neutral,publickeytoken=b77a5c561394e089 failed.

please tell me what should i do.

thanks in advance...... Big Grin | :-D

Christian Graus19-Jun-09 10:59

19-Jun-09 10:59

Try here[^]

Rits11038920-Jun-09 1:27