拖放树视图到gridview的麻烦 [英] Trouble with a drag and drop treeview to gridview
本文介绍了拖放树视图到gridview的麻烦的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
早上好，
我想使用TreeView可以在GridView中拖放
我制作TreeView但是当想要拖放我的时候有一个问题是null异常，4天后我看不到问题。
让我告诉你我的代码来帮助我。
我有一个类库LabelData来创建数据库和数据类
这是我的桌子
< pre lang =sql> ;
CREATE TABLE MyTable
（IdTable Int（2），
IdLabel Int（20），
LName char（50）
）
< pre lang =sql> INSERT INTO MyTable（IdTable，IdLabel，LName）VALUES（1,200，'firstName'）;
INSERT INTO MyTable（IdTable，IdLabel，LName）VALUES（2,200，'lastName'）;
INSERT INTO MyTable（IdTable，IdLabel，LName）VALUES（3,200，'middleName'）;
INSERT INTO MyTable（IdTable，IdLabel，LName）VALUES（4,201，'circuit'）;
INSERT INTO MyTable（IdTable，IdLabel，LName）VALUES（5,201，'series'）;
INSERT INTO MyTable（IdTable，IdLabel，LName）VALUES（6,202，'country'）;
INSERT INTO MyTable（IdTable，IdLabel，LName）VALUES（7,202，'region'）;
INSERT INTO MyTable（IdTable，IdLabel，LName）VALUES（8,202，'zipcode'）;
为了制作树视图，我使用IdLabel制作类别，我使用LName制作产品。
我在我的桌子上添加了一个遗产MyTable GroupLabel，属性LName
这是我的班级data.cs
使用System;
使用System.Collections.Generic;
使用System.Linq;
使用System.Text;
LNamespace LabelData
{
public class DataProvider
{
LabelDataContext dc;
public DataProvider（）
{
dc = new LabelDataContext（）;
}
public IEnumerable< Label> GetLabel（）
{
从e.IdLabel的dc.MyTable
组e中返回到gr
选择新标签（）{IdLabel = gr.Key，LName = gr };
}
public IEnumerable< MyTable> Get_Table（）
{
从dc返回p.TyTable
select p;
}
}
公共类标签
{
public int IdLabel {得到;组; }
public IEnumerable< MyTable> LName {get;组; }
}
}
Goldoni
发表于33分钟前（固定链接）
早上好，
我想使用可以在GridView中拖放的TreeView
我制作TreeView但是当想要拖放我有一个问题时出现null异常，4天后我看不到问题。
让我告诉你我的代码来帮助我。
我有一个类库LabelData来创建数据库和数据类
这是我的表
CREATE TABLE MyTable
（IdTable Int（2），
IdLabel Int（20），
LName char（50）
）
和我的行
INSERT INTO MyTable（IdTable） ，IdLabel，LName）VALUES（1,200，'firstName'）;
INSERT INTO MyTable（IdTable，IdLabel，LName）VALUES（2,200，'lastName'）;
INSERT INTO MyTable（IdTable，IdLabel，LName）VALUES（3,200，'middleName'）;
INSERT INTO MyTable（IdTable，IdLabel，LName）VALUES（4,201，'circuit'）;
INSERT INTO MyTable（IdTable，IdLabel，LName）VALUES（5,201，'series'）;
INSERT INTO MyTable（IdTable，IdLabel，LName）VALUES（6,202，'country'）;
INSERT INTO MyTable（IdTable，IdLabel，LName）VALUES（7,202，'region'）;
INSERT INTO MyTable（IdTable，IdLabel，LName）VALUES（8,202，'zipcode'）;
为了进行树视图，我使用IdLabel制作像类别，我使用LName制作产品。
我在我的桌子上添加一个遗产MyTable GroupLabel，属性LName
这是我的班级data.cs
使用System;
使用System.Collections.Generic;
使用System.Linq;
使用System.Text;
LNamespace LabelData
{
public class DataProvider
{
LabelDataContext dc;
public DataProvider（）
{
dc = new LabelDataContext（）;
}
public IEnumerable< Label> GetLabel（）
{
从e.IdLabel的dc.MyTable
组e中返回到gr
选择新标签（）{IdLabel = gr.Key，LName = gr };
}
public IEnumerable< MyTable> Get_Table（）
{
从dc返回p.TyTable
select p;
}
}
公共类标签
{
public int IdLabel {得到;组; }
public IEnumerable< MyTable> LName {get;组; }
}
}
这是我的代码xaml.cs
使用System;
使用System.Collections.Generic;
使用System.Linq;
使用System.Text;使用System.Windows
;
使用System.Windows.Data;
使用System.Windows.Documents;
使用System.Windows.Input;
使用System.Windows.Media;
使用System.Windows.Media.Imaging;使用System.Windows.Navigation
;
使用System.Windows.Shapes;
使用Telerik.Windows.Controls.GridView;
使用Telerik.Windows.Controls.DragDrop;
使用Telerik.Windows.Controls;
使用System.Collections.ObjectModel;
使用LabelData;
使用Telerik.Windows.Controls.TreeView;
使用System.Collections;
使用System.Net;使用System.Windows.Media.Animation
;使用Telerik.Windows
;
LNamespace LabelMunich
{
///< summary>
/// Logique d'interaction pour MainWindow.xaml
///< / summary>
public partial class WindowTreeView：Window
{
public WindowTreeView（）
{
InitializeComponent（）;
ProfilData.DataProvider dataProvider = new ProfilData.DataProvider（）;
treeView1.ItemsSource = dataProvider.GetModule（）;
radGridView.ItemsSource = dataProvider.Get_Table（）;
RadDragAndDropManager.AddDropQueryHandler（radGridView，new EventHandler< DragDropQueryEventArgs>（this.RadGridView_OnDropQuery））;
RadDragAndDropManager.AddDropInfoHandler（radGridView，new EventHandler< DragDropEventArgs>（this.RadGridView_OnDropInfo））;
}
private void RadRibbonButton_Click（object sender，RoutedEventArgs e）
{
// FAjout fa = new FAjout（）;
formAjout fa = new formAjout（）;
fa.Show（）;
// this.ShowActivated（）;
}
private void radTreeView_PreviewDragEnded（object sender，RadTreeViewDragEndedEventArgs e）
{
e.Handled = true;
}
private void RadGridView_OnDropQuery（object sender，DragDropQueryEventArgs e）
{
e.QueryResult =（e.Options.Source as RadTreeViewItem）。项目是模块;
}
private void RadGridView_OnDropInfo（object sender，DragDropEventArgs e）
{
if（e.Options.Status == DragStatus.DropComplete）
{
（radGridView.ItemsSource为IList< Module>）。添加（（e.Options.Payload as Collection< Object>）[0]作为模块）;
}
}
}
}
和我的Xaml文件
< pre lang =xml>< Window x：Class =ProfilTandem.WindowTreeView
xmlns =http：// schemas。 microsoft.com/winfx/2006/xaml/presentation
xmlns：x =http://schemas.microsoft.com/winfx/2006/xaml
xmlns：northwind =clr-namespace： ProfilData; assembly = LabelData
xmlns：local =clr-namespace：LabelMunich
xmlns：telerik =http://schemas.telerik.com/2008/xaml/presentation
xmlns：telerikDragDrop =clr-namespace：Telerik.Windows.Controls.DragDrop; assembly = Telerik.Windows.Controls
Title =MainWindowHeight =450Width =585>
< Window.Resources>
< DataTemplate x：Key =Team>
< TextBlock Text ={Binding Path = LName}/>
< / DataTemplate>
< HierarchicalDataTemplate DataType ={x：Type northwind：Label}ItemsSource ={Binding Path = LName}>
< Border Width =250>
< Grid>
< TextBlock
Text ={Binding Path = IdLabel}FontSize =14FontWeight =BoldMargin =2>
< / TextBlock>
< / Grid>
< / Border>
< / HierarchicalDataTemplate>
< HierarchicalDataTemplate DataType ={x：Type northwind：GroupLabel}>
< Grid Margin =6>
< TextBlock Text ={Binding Path = LName}Padding =2/>
< / Grid>
< / HierarchicalDataTemplate>
< /Window.Resources>
< Grid>
< Grid.ColumnDefinitions>
< ColumnDefinition Width =*/>
< ColumnDefinition Width =*/>
< /Grid.ColumnDefinitions>
< Grid.RowDefinitions>
< RowDefinition Height =Auto/>
< RowDefinition Height =Auto/>
< /Grid.RowDefinitions>
< telerik：RadTreeView IsDragDropEnabled =TrueGrid.Column =0Grid.Row =1
SelectionMode =MultipleIsEditable =Truex：Name = treeView1Margin =0,20,0,245
PreviewDragEnded =radTreeView_PreviewDragEnded
IsDragTooltipEnabled =FalseItemsSource ={Binding}/>
< StackPanel Grid.Column =1Grid.Row =1>
< telerik：RadGridView x：Name =radGridViewAutoGenerateColumns =False
Width =400Height =400HorizontalAlignment =LefttelerikDragDrop：RadDragAndDropManager.AllowDrop =True
DataContext ={Binding}ItemsSource ={Binding}>
< telerik：RadGridView.Columns>
< telerik：GridViewDataColumn DataMemberBinding ={Binding Path = IdLabel}/>
< telerik：GridViewDataColumn DataMemberBinding ={Binding Path = LName}/>
< / telerik：RadGridView.Columns>
< / telerik：RadGridView>
< / StackPanel>
< / Grid>
< / Window>
这就是全部
当我尝试将项目树视图拖到gridview时，我在这条线上有例外
（radGridView.ItemsSource为IList< Label>）。添加（（e.Options.Payload as Collection< Object>）[0] as Label）;
异常System.NullReferenceException未处理
对象引用未设置为对象的实例
感谢您的帮助
解决方案
只需运行调试器即可。它看起来像radGridView.ItemsSource是null或者它的类型没有实现接口IList< ; Label>，它将返回as运算符的null结果。检查您分配ItemsSource的位置及其类型。在你的代码中，不要在这一行中做出隐含的假设。
-SA
< blockquote>你可以找到一篇在这里完成这项工作的文章。
http://gonetdotnet.blogspot.in/2014/09/solved-how-to-drag-and-drop-items-from.html
Good morning,
I would like to use a TreeView that's can drag and drop in a GridView
I make the TreeView but when a want to drag and drop i have a probleme the null Exception, after 4 days i can't see the problem.
Let me show you my code to help me please.
I have a class library LabelData to make the database and a data class
this is my table
<pre lang="sql"> CREATE TABLE MyTable (IdTable Int(2), IdLabel Int(20), LName char(50) )
<pre lang="sql">INSERT INTO MyTable (IdTable,IdLabel,LName) VALUES (1, 200, 'firstName'); INSERT INTO MyTable (IdTable,IdLabel,LName) VALUES (2, 200, 'lastName'); INSERT INTO MyTable (IdTable,IdLabel,LName) VALUES (3, 200, 'middleName'); INSERT INTO MyTable (IdTable,IdLabel,LName) VALUES (4, 201, 'circuit'); INSERT INTO MyTable (IdTable,IdLabel,LName) VALUES (5, 201, 'series'); INSERT INTO MyTable (IdTable,IdLabel,LName) VALUES (6, 202, 'country'); INSERT INTO MyTable (IdTable,IdLabel,LName) VALUES (7, 202, 'region'); INSERT INTO MyTable (IdTable,IdLabel,LName) VALUES (8, 202, 'zipcode');
For make the treeview, I use IdLabel to make like "categorie" and i use LName to make like "product" .
I add a heritance in on my table MyTable GroupLabel with the property LName
This is my class data.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
LNamespace LabelData
{
public class DataProvider
{
LabelDataContext dc;
public DataProvider()
{
dc = new LabelDataContext();
}
public IEnumerable<Label> GetLabel()
{
return from e in dc.MyTable
group e by e.IdLabel into gr
select new Label() { IdLabel = gr.Key, LName= gr };
}
public IEnumerable<MyTable> Get_Table()
{
return from p in dc.MyTable
select p;
}
}
public class Label
{
public int IdLabel { get; set; }
public IEnumerable<MyTable> LName{ get; set; }
}
}
Goldoni
Posted 33 minutes ago (permalink)
Good morning,
I would like to use a TreeView that's can drag and drop in a GridView
I make the TreeView but when a want to drag and drop i have a probleme the null Exception, after 4 days i can't see the problem.
Let me show you my code to help me please.
I have a class library LabelData to make the database and a data class
this is my table
CREATE TABLE MyTable (IdTable Int(2), IdLabel Int(20), LName char(50) )
and my Rows
INSERT INTO MyTable (IdTable,IdLabel,LName) VALUES (1, 200, 'firstName'); INSERT INTO MyTable (IdTable,IdLabel,LName) VALUES (2, 200, 'lastName'); INSERT INTO MyTable (IdTable,IdLabel,LName) VALUES (3, 200, 'middleName'); INSERT INTO MyTable (IdTable,IdLabel,LName) VALUES (4, 201, 'circuit'); INSERT INTO MyTable (IdTable,IdLabel,LName) VALUES (5, 201, 'series'); INSERT INTO MyTable (IdTable,IdLabel,LName) VALUES (6, 202, 'country'); INSERT INTO MyTable (IdTable,IdLabel,LName) VALUES (7, 202, 'region'); INSERT INTO MyTable (IdTable,IdLabel,LName) VALUES (8, 202, 'zipcode');
For make the treeview, I use IdLabel to make like "categorie" and i use LName to make like "product" .
I add a heritance in on my table MyTable GroupLabel with the property LName
This is my class data.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
LNamespace LabelData
{
public class DataProvider
{
LabelDataContext dc;
public DataProvider()
{
dc = new LabelDataContext();
}
public IEnumerable<Label> GetLabel()
{
return from e in dc.MyTable
group e by e.IdLabel into gr
select new Label() { IdLabel = gr.Key, LName= gr };
}
public IEnumerable<MyTable> Get_Table()
{
return from p in dc.MyTable
select p;
}
}
public class Label
{
public int IdLabel { get; set; }
public IEnumerable<MyTable> LName{ get; set; }
}
}
And this is my behind code xaml.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using Telerik.Windows.Controls.GridView;
using Telerik.Windows.Controls.DragDrop;
using Telerik.Windows.Controls;
using System.Collections.ObjectModel;
using LabelData;
using Telerik.Windows.Controls.TreeView;
using System.Collections;
using System.Net;
using System.Windows.Media.Animation;
using Telerik.Windows;
LNamespace LabelMunich
{
/// <summary>
/// Logique d'interaction pour MainWindow.xaml
/// </summary>
public partial class WindowTreeView : Window
{
public WindowTreeView()
{
InitializeComponent();
ProfilData.DataProvider dataProvider = new ProfilData.DataProvider();
treeView1.ItemsSource = dataProvider.GetModule();
radGridView.ItemsSource = dataProvider.Get_Table();
RadDragAndDropManager.AddDropQueryHandler(radGridView, new EventHandler<DragDropQueryEventArgs>(this.RadGridView_OnDropQuery));
RadDragAndDropManager.AddDropInfoHandler(radGridView, new EventHandler<DragDropEventArgs>(this.RadGridView_OnDropInfo));
}
private void RadRibbonButton_Click(object sender, RoutedEventArgs e)
{
// FAjout fa = new FAjout();
formAjout fa = new formAjout();
fa.Show();
// this.ShowActivated();
}
private void radTreeView_PreviewDragEnded(object sender, RadTreeViewDragEndedEventArgs e)
{
e.Handled = true;
}
private void RadGridView_OnDropQuery(object sender, DragDropQueryEventArgs e)
{
e.QueryResult = (e.Options.Source as RadTreeViewItem).Item is Module;
}
private void RadGridView_OnDropInfo(object sender, DragDropEventArgs e)
{
if (e.Options.Status == DragStatus.DropComplete)
{
(radGridView.ItemsSource as IList<Module>).Add((e.Options.Payload as Collection<Object>)[0] as Module);
}
}
}
}
And my Xaml document
<pre lang="xml"><Window x:Class="ProfilTandem.WindowTreeView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:northwind="clr-namespace:ProfilData;assembly=LabelData"
xmlns:local="clr-namespace:LabelMunich"
xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation"
xmlns:telerikDragDrop="clr-namespace:Telerik.Windows.Controls.DragDrop;assembly=Telerik.Windows.Controls"
Title="MainWindow" Height="450" Width="585">
<Window.Resources>
<DataTemplate x:Key="Team">
<TextBlock Text="{Binding Path=LName}"/>
</DataTemplate>
<HierarchicalDataTemplate DataType="{x:Type northwind:Label}" ItemsSource="{Binding Path=LName}">
<Border Width="250">
<Grid>
<TextBlock
Text="{Binding Path=IdLabel}" FontSize="14" FontWeight="Bold" Margin="2" >
</TextBlock>
</Grid>
</Border>
</HierarchicalDataTemplate>
<HierarchicalDataTemplate DataType="{x:Type northwind:GroupLabel}">
<Grid Margin="6">
<TextBlock Text="{Binding Path=LName}" Padding="2" />
</Grid>
</HierarchicalDataTemplate>
</Window.Resources>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<telerik:RadTreeView IsDragDropEnabled="True" Grid.Column="0" Grid.Row="1"
SelectionMode="Multiple" IsEditable="True" x:Name="treeView1" Margin="0,20,0,245"
PreviewDragEnded="radTreeView_PreviewDragEnded"
IsDragTooltipEnabled="False" ItemsSource="{Binding}"/>
<StackPanel Grid.Column="1" Grid.Row="1">
<telerik:RadGridView x:Name="radGridView" AutoGenerateColumns="False"
Width="400" Height="400" HorizontalAlignment="Left" telerikDragDrop:RadDragAndDropManager.AllowDrop="True"
DataContext="{Binding}" ItemsSource="{Binding}">
<telerik:RadGridView.Columns>
<telerik:GridViewDataColumn DataMemberBinding="{Binding Path=IdLabel}"/>
<telerik:GridViewDataColumn DataMemberBinding="{Binding Path=LName}"/>
</telerik:RadGridView.Columns>
</telerik:RadGridView>
</StackPanel>
</Grid>
</Window>
This is all
When i try to drag items treeview to gridview i have exception on this line
(radGridView.ItemsSource as IList<Label>).Add((e.Options.Payload as Collection<Object>)[0] as Label);
The exception System.NullReferenceException was unhandled
Object reference not set to an instance of an object
Thank you for your help
解决方案
Just run with the debugger ans see. It looks like eitherradGridView.ItemsSourceisnullor its type does not implement the interfaceIList<Label>which would return null result of the as operator. Check where you assignItemsSourceand its type. In your code, don't make implicit assumptions you made in this line.
—SA
you can find an article which does this job here.
http://gonetdotnet.blogspot.in/2014/09/solved-how-to-drag-and-drop-items-from.html
这篇关于拖放树视图到gridview的麻烦的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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