I have two pages sharing the same Dropdown control which need the same logic for filling the Dropdown. The code looks like:
private void FillDropDown(Guid indentifier)
{
DateTime start = GetStartFromSession;
DateTime end = GetEndFromSession;
List<DataToDisplay> dataToDisplay = Businesslogic.GetData(identifier, start,end);
dataToDisplay.Add(new DataToDisplay(){ID : Guid.Empty, Value: GetLocalResourceString("PleaseSelectText");
//some more logic....
dropDown.DataSource = dataToDisplay;
dropDown.DataBind();
}
The code is exactly the same in two pages. I am not a fan of creating a helper class which needs the Businesslogic, the control to fill etc. But as code duplication is bad, i don't like the current solution also. I was thinking about creating a new generic control but its only a Dropdownbox, nothing more.
Any ideas?
Thanks
I'm writing an application for windows ce, so I have to use VS 2008.
I'm showing some Data in a dataGrid-Control (DataGridView NOT available!), and I want to customize it.
things like grid.Columns[i].width etc are not working on these controls.
I need to change the columns width and header texts, how can I achieve that?
The datagrid gets it entries at runtime with this line:
dgLatestPositions.DataSource = items;
items is a list<> containing objects, the table got 2 columns.
The view of the dataGrid is working fine, except these issues.
edit: Maybe something like that? (It's not working yet either)
DataGridTableStyle t = new DataGridTableStyle();
t.GridColumnStyles[0].HeaderText = "Coding";
t.GridColumnStyles[1].HeaderText = "Amount";
dgLatestPositions.TableStyles.Add(t);
Edit:
All Items are contained in a List.
The article-objects looks this way:
public class lastChanges
{
public long coding { get; set; }
public int amount { get; set; }
}
The Table shows up like this (example)
coding |amount
0123456789|3
0829346128|4
What I need to do is resize the first column and change the captions
We too have an app that requires back support under WindowsCE and has to be done in VS2008. You are very close, and what we did was created a base-class data grid for display and added a method to add the columns we wanted getting the heading text, binding column source and then the width. Here is our method and the "myTblStyle" is your DataGridTableStyle "t" variable.
public void AddColumn(string hdr, string colName, int colWidth)
{
DataGridTextBoxColumn tbc = new DataGridTextBoxColumn();
tbc.HeaderText = hdr;
tbc.MappingName = colName;
tbc.Width = colWidth;
myTblStyle.GridColumnStyles.Add(tbc);
}
I have a list of Strings.
Well, conceptually. They are stored somewhere else, but I want provide an object which acts like a list (and provides any necessary events on top of that), with properties that I could bind to.
I want to establish a two-way binding over this data, to display it as a modifiable column in a DataGrid. I have the following problems with that:
I can't make a two-way binding because the binding needs a path (i.e. I can't have it look like {Binding} or {Binding Path=.} in the column, must be {Binding Path=someField"} to be made modifiable if I got this right, which sounds reasonable).
I don't exactly know how the proxy collection object should look like, in terms of interfaces (would IEnumerable + INotifyCollectionChanged sufficient?)
Is there any solution which doesn't involve creating one proxy object per every String in the collection? Could you suggest an efficient design?
To keep the discussion on the rails, let's assume I want to bind to something like this:
class Source {
public String getRow(int n);
public void setRow(int n, String s);
public int getCount();
public void addRow(int position, String s);
public void removeRow(int position);
}
That's not exactly my case, but when I know how to bind to this, I think I'll be able to handle any situation like this.
I'm OK with having to provide an adapter object on top of that Source, with any necessary interfaces and events, but I don't want to have one adapter object per row of data.
While making an adapter for the Source is relatively clear, then, unfortunatelly, the core of the second problem ('not wrapping every string in a miniobject') is a clash built into the .Net and WPF..
The first thing is that the WPF does provide you with many ways of registering 'on data modified' callbacks, but provides no way of registering callbacks that would provide a value. I mean, the "set" phase is only extendable, not interceptable, and the "get" - nothing at all. WPF will simply keep and return whatever data it has once cached.
The second thing is that in .Net the string is ... immutable.
Now, if ever you provide a string directly as a pathless binding or as a datacontext to any control, you are screwed in a dead end. The problem is, that WPF actually passes only the actual value of the binding, without the information of "where it came from". The underlying control will be simply given the string instance, and will have no sane way of modifying it as the string cannot change itself. You will not be even notified about such attempt, just like with read-only properties. What's more - if you ever manage to intercept such a modification attempt, and if you produce a proper new string, the WPF will never ask you again for the new value. To update the UI, you'd have to mannually, literally, force the WPF to re-ask you by for example changing the original binding so it points elsewhere (to the new value) or set the datacontext (to the new instance). It is doable with some VisualTree scanning, as every 'changed' callback gives you the DependencyObjects (Controls!), so yo ucan scan upwards/downwards and tamper with their properties.. Remember that option - I'll refer to this in a minute.
So, everything boils down to the fact that to get a normal 2-way binding you do not have to have a Path, you "just" have to have a mutable underlying data object. If you have immutable one - then you have to use a binding to a mutable property that holds the immutable value..
Having said that, you simply have to wrap the strings some how if you want to modify them.
The other question is, how to do that. There's a plenty of ways to do it. Of course, you can simply wrap them like Joe and Davio suggested (note to Joe: INotify would be needed there also), or you can try to do some XAML tricks with attached properties and/or behaviours and/or converters to do that for you. This is completely doable, see for example my other post - I've shown there how to "inject a virtual property" that pulled the data completely from elsewhere (one binding+converter performed the wrapping on the fly, second binding extracted the values from the attached-wrapper). This way you could create a "Contents" property on the string, and that property could simply return the string itself, and it'd be completely 2-way bindable with no exceptions.
But.. it would NOT work 2-way-ish.
Somewhere at the root of your binding/behaviour/conveter chain, there will be an immutable string. Once your smart autowrapping binding chain fires with 'on modified' callback you will be notified with pair of old/new values. You will be able to remap the values to new and old strings. If you implemented everything perfectly, the WPF will simply use the new value. If you tripped somewhere, then you will have to push the new value artificially back to the UI (see the options I'd asked you to remember). So, it's ok. No wrapper, old value was visible, it was changeable, you've got new value, the UI displays new value. How about storage?
Somewhere in the meantime you've been given a old/new value pair. If you analyze them, you'll get old/new strings. But how do you update the old immutable string? Can't do. Even if autowrapping worked, even if UI worked, even if editing seemed to work, you are now standing with the real task: you onmodified callback was invoked and you have to actually update that immutable string piece.
First, you need your Source. Is it static? Phew. What a luck! So surely it is instanced. In the on-modified callback we got only a old+new string.. how to get the Source instance? Options:
scan the VisualTree and search for it in the datacontexts and use whatever was found..
add some more attached properties and binding to bind a virtual "Source" property to every string and read that property from the new value
Well doable, but smells, but no other options.
Wait, there's more: not only the old/new value and an instance of Source are needed! You also need the ROW INDEX. D'oh! how to get that from the bound data? Again, options:
scan the VisualTree and search for it (blaargh)...
add some more attached properties and bindings to bind a virtual "RowIndex" property to every (blaaergh)...
At this point of time, while I see that all of this seems implementable and actually might be working properly, I really think that wrapping each string in a small
public class LocalItem // + INotifyPropertyChanged
{
public int Index { get; }
public Source Source { get; }
public string Content
{
get { Source...}
set { Source... }
}
}
will simply be more readable, elegant and .. SHORTER to implement. And less error-prone, as more details will be explicit instead of some WPF's binding+attached magic..
I find your approach a little weird.
DataGrids are usually used to display Rows. Rows consist of data that belongs together.
You could for instance easily map a row to a certain class. This means that the columns in your datagrid represent properties in your class.
What you're trying to do is the opposite, you're trying to get a relation between the column values instead of the row values.
Wouldn't it be easier to have a collection of your class which you can then bound the column to?
For instance
class MyClass : INotifyPropertyChanged
{
// Remember to actually implement INotifyPropertyChanged
string Column;
}
If you would have an ObservableCollection of MyClass you could bind the DataGrid to this collection. Whenever the property which I called "Column" changes, you could update your special list.
You can do this by hooking up some events. With the implementation of INotifyPropertyChanged, your columns will be updated if you update the "Column"-value directly.
I have this bit of code I use to bind a list of custom object to a DataContextMenu. You can alter it to use a list of strings and bind it to what you need
class SampleCode
{
class Team
{
private string _TeamName = "";
private int _TeamProperty1 = 0;
ObservableCollection<Territory> _Territories = new ObservableCollection<Territory>();
public Team(string tName)
{
this.TeamName = tName;
}
public ObservableCollection<Territory> Territories
{
get { return _Territories; }
set { _Territories = value; }
}
public string TeamName
{
get { return _TeamName; }
set { _TeamName = value; }
}
public int TeamProperty1
{
get { return _TeamProperty1; }
set { _TeamProperty1 = value; }
}
}
class Territory
{
private string _TerritoryName = "";
Team _AssociatedTeam = null;
public Territory(string tName, Team team)
{
this.TerritoryName = tName;
this.AssociatedTeam = team;
}
public Team AssociatedTeam
{
get { return _AssociatedTeam; }
set { _AssociatedTeam = value; }
}
public string TerritoryName
{
get { return _TerritoryName; }
set { _TerritoryName = value; }
}
public void Method1()
{
//Do Some Work
}
}
class MyApplication
{
ObservableCollection<Team> _Teams = new ObservableCollection<Team>();
ContextMenu _TeritorySwitcher = new ContextMenu();
public MyApplication()
{
}
public void AddTeam()
{
_Teams.Add(new Team("1"));
_Teams.Add(new Team("2"));
_Teams.Add(new Team("3"));
_Teams.Add(new Team("4"));
foreach (Team t in _Teams)
{
t.Territories.Add(new Territory("1", t));
t.Territories.Add(new Territory("2", t));
t.Territories.Add(new Territory("3", t));
}
SetContextMenu();
}
private void SetContextMenu()
{
HierarchicalDataTemplate _hdtTerritories = new HierarchicalDataTemplate();
_hdtTerritories.DataType = typeof(Territory);
HierarchicalDataTemplate _hdtTeams = new HierarchicalDataTemplate();
_hdtTeams.DataType = typeof(Team);
FrameworkElementFactory _TeamFactory = new FrameworkElementFactory(typeof(TreeViewItem));
_TeamFactory.Name = "txtTeamInfo";
_TeamFactory.SetBinding(TreeViewItem.HeaderProperty, new Binding("TeamProperty1"));
FrameworkElementFactory _TerritoryFactory = new FrameworkElementFactory(typeof(TreeViewItem));
_TerritoryFactory.Name = "txtTerritoryInfo";
_TerritoryFactory.SetBinding(TreeViewItem.HeaderProperty, new Binding("TerritoryProperty1"));
_hdtTeams.ItemsSource = new Binding("Territories");
_hdtTeams.VisualTree = _TeamFactory;
_hdtTerritories.VisualTree = _TerritoryFactory;
_hdtTeams.ItemTemplate = _hdtTerritories;
_TeritorySwitcher.ItemTemplate = _hdtTeams;
_TeritorySwitcher.ItemsSource = this._Teams;
}
}
}
Lazy solution
Derive from ObservableCollection<string> and let that collection be populated from the Source. In the derived class, register to collection change events and update the source accordingly. Bind the DataGrid column to the observable collection.
This should be pretty straightforward to write, but has a big drawback of duplicating all data in the collection.
More efficient solution
Create an adapter (as you suggested) and implement IList<string> and INotifyCollectionChanged. Let the list operations fall through directly to the source. Bind the DataGrid column to the adapter.
This approach would require some tedious boilerplate, but it's a thin layer between the WPF control and your Source.
This really depends on how you're implementing the UI. Bea Stollnitz did an excellent post of virtualizing the ItemsSource for the WPF DataGrid at http://bea.stollnitz.com/blog/?p=344 . With work I used this to edit as well as display data.
The easiest way is by placing the string in a wrapper class.
public class Wrapper
{
public string Content{get;set;}
}
Then you use the string via the wrapper class. This was the list items remain the same but the content changes.
The problem is when you do this without that then an old string is being deleted and a new one is created and the collection is confused.
Start with an ObservableCollection<string>. Then set the bindable control's ItemsSource to the ObservableCollection.
I have an ItemsControl displaying a collection of files. Those files are sorted by most recent modification, and there's a lot of them.
So, I want to initially only show a small part (say, only 20 or so) of them, and display a button labelled "Show More" that would reveal everything when clicked.
I already have a solution, but it involves using a good old LINQ Take on my view model's source property. I was wondering if there was a cleaner way.
Thanks.
Why not have the object that you assign to the ItemsSource handle this logic - on first assignment, it would report a limited subset of the items. When Show More is clicked, the object is updated to show more (or all entries) and then notifies the framework that the property has changed (e.g. using the IPropertyNotifyChanged).
public class MyItemSource
{
private List<string> source = { ... };
public MyItemSource()
{
this.ShowThisMany = 20;
}
public int ShowThisMany
{
get;
set; // this should call\use the INotifyPropertyChanged interface
}
public IEnumerable<string> this[]
{
return this.source.Take(this.ShowThisMany);
}
}
...
MyItemsSource myItemsSource = new MyItemsSource();
ItemsControl.Source = myItemsSource;
...
void OnShowMoreClicked(...)
{
myItemsSource.ShowThisMany = 50;
}
In order to do this, you need to create some sort of 'view' on your data. There is nothing within the WPF framwork that will give you this functionality for free. In my opinion, a simple bit of Linq, Take(), is a clean and simple solution.
I've got the following code which I think ought to be binding a DataTable to a DataGridView, but the DataGridView shows up empty. The DataTable definately has rows, so I assume that I am binding the DataSource incorrectly some how. Does anyone see what is wrong with this:
DataBase db = new DataBase(re.OutputDir+"\\Matches.db");
MatchDBReader reader = new MatchDBReader(db.NewConnection());
BindingSource bindingSource = new BindingSource();
bindingSource.DataSource = reader.GetDataTable();
this.dataGridView1.DataSource = bindingSource.DataSource;
The first line simply gets a handle to the DB that I'm pulling data from.
The next line is a provides a class for reading from that same db - in particular it exposes the GetDataTable method with returns the data table that I intend to put into the DataGridView.
The next line is uninteresting...
The 4th line attempts to grab the DataTable - QuickWatch indicates that this is working...
The final line is where I assume i've screwed up...my understanding is that this binds the DataTable to the DataGridView GUI, but nothing shows up.
Any thoughts?
Try binding the DataGridView directly to the BindingSource, and not the BindingSource's DataSource:
this.dataGridView1.DataSource = bindingSource;
You need to attach your BindingSource to your grid, before you get the data table.
Try switching the last two lines of code:
DataBase db = new DataBase(re.OutputDir+"\\Matches.db");
MatchDBReader reader = new MatchDBReader(db.NewConnection());
BindingSource bindingSource = new BindingSource();
this.dataGridView1.DataSource = bindingSource.DataSource;
bindingSource.DataSource = reader.GetDataTable();
Along with above solutions also fix the "bindingSource" datamember property. like:
bindingSource.DataMember = yourDataSet.DataTable;
I had the same problem with sql database and datagrid view. After a great deal of trouble I found out that I've forgot to set dataMember property of my binding source.
best of luck.
None of this worked for me, though it all seemed like good advice. What I ended up doing was the biggest, worst hack on earth. What I was hoping to accomplish was simply to load a DB table from a SQLite db and present it (read only, with sortable columns) in the DataGridView. The actual DB would be programmatically specified at runtime. I defined the DataSet by adding a DataGridView to the form and used the Wizards to statically define the DB connection string. Then I went into the Settings.Designer.cs file and added a set accessor to the DB Connection string property:
namespace FormatDetector.Properties {
[global::System.Runtime.CompilerServices.CompilerGeneratedAttribute()]
[global::System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.VisualStudio.Editors.SettingsDesigner.SettingsSingleFileGenerator", "9.0.0.0")]
internal sealed partial class Settings : global::System.Configuration.ApplicationSettingsBase {
private static Settings defaultInstance = ((Settings)(global::System.Configuration.ApplicationSettingsBase.Synchronized(new Settings())));
public static Settings Default {
get {
return defaultInstance;
}
}
[global::System.Configuration.ApplicationScopedSettingAttribute()]
[global::System.Diagnostics.DebuggerNonUserCodeAttribute()]
[global::System.Configuration.SpecialSettingAttribute(global::System.Configuration.SpecialSetting.ConnectionString)]
[global::System.Configuration.DefaultSettingValueAttribute("data source=E:\\workspace\\Test\\Matches.db;useutf16encoding=True")]
public string MatchesConnectionString {
get {
return ((string)(this["MatchesConnectionString"]));
}
set
{
(this["MatchesConnectionString"]) = value;
}
}
}
}
This is a klugey hack, but it works. Suggestions about how to clean this mess up are more than welcome.
brian
DataGridView takes a DataTable as a basis. The DataTable Columns save their Type as a property.
If this type is an Interface all you would see are empty cells.