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POWpf datagrid changing state from readonly to editable at runtime
 

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  1. POWpf datagrid changing state from readonly to editable at runtime
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    <p>I am new to WPF development yet. I just quickly created a sample to recreate the scenario. I am switching the IsReadonly Property of the datagrid in rowdetailsview based on the checkbox in the parent row.</p> <p>Everything works fine except in one particular scenario.</p> <p>How to recreate problem.</p> <p>Keep the initially create parent row checked. uncheck the parent row. go to the child row id property. clean everything in id field and tab out of that cell and you will see null reference exception.</p> <p>I have no clue how to fix this issue. Any insight will be really useful. </p> <p>code behind code:</p> <pre><code> namespace WpfApplication7 {/// &lt;summary&gt; /// Interaction logic for MainWindow.xaml /// &lt;/summary&gt; public partial class MainWindow : Window { public PerColl People { get; private set; } public MainWindow() { InitializeComponent(); this.People = new PerColl(); this.DataContext = this; } private void Button_Click(object sender, RoutedEventArgs e) { } public class Person : INotifyPropertyChanged, IEditableObject { public string Name { get; set; } public double Salary { get { return _salary; } set { if (this._salary == value) return; this._salary = value; if (this.PropertyChanged != null) this.PropertyChanged(this, new PropertyChangedEventArgs("Salary")); } } public bool IsLocked { get { return _isLocked; } set { if (this._isLocked == value) return; this._isLocked = value; if (this.PropertyChanged != null) this.PropertyChanged(this, new PropertyChangedEventArgs("IsLocked")); } } public ObservableCollection&lt;Kid&gt; Kids { get; set; } public Person(string name, double salary) { this.Name = name; this.Salary = salary; } public Person() { this.Salary = 10000; this.Name = "abc"; this.IsLocked = true; this.Kids = new ObservableCollection&lt;Kid&gt;(); this.Kids.Add(new Kid(1)); this.Kids.Add(new Kid(2)); } private bool _isLocked; private double _salary; #region INotifyPropertyChanged Members public event PropertyChangedEventHandler PropertyChanged; #endregion public void BeginEdit() { if (isEdit) return; isEdit = true; this.backup = this.MemberwiseClone() as Person; } public void CancelEdit() { if (!this.isEdit) return; isEdit = false; this.Name = this.backup.Name; this.Salary = this.backup.Salary; } public void EndEdit() { if (this.isEdit == false) return; this.isEdit = false; this.backup = null; } private bool isEdit; private Person backup; } public class PerColl : ObservableCollection&lt;Person&gt; { } public class Kid : IEditableObject,INotifyPropertyChanged { public int Id { get { return _id; } set { this._id = value; if (PropertyChanged != null) this.PropertyChanged(this, new PropertyChangedEventArgs("Id")); } } public string Name { get { return _name; } set { this._name = value; if (PropertyChanged != null) this.PropertyChanged(this, new PropertyChangedEventArgs("Name")); } } public Person Parent { get; set; } public Kid() { this.Id = 12345; this.Name = "kidname"; } public Kid(int id, string name = "kidname") { this.Id = 12345; this.Name = name; } #region IEditableObject Members public void BeginEdit() { if (isEdit) return; isEdit = true; this.backup = this.MemberwiseClone() as Kid; } public void CancelEdit() { if (!this.isEdit) return; isEdit = false; this.Id = backup.Id; } public void EndEdit() { if (this.isEdit == false) return; this.isEdit = false; this.backup = null; } #endregion private int _id; private string _name; private bool isEdit; private Kid backup; #region INotifyPropertyChanged Members public event PropertyChangedEventHandler PropertyChanged; #endregion } } } </code></pre> <p>Xaml Code:</p> <pre><code>&lt;Window x:Class="WpfApplication7.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="MainWindow" Height="350" Width="525"&gt; &lt;DockPanel LastChildFill="True" Margin="-1,5,1,-5"&gt; &lt;Button Content="Add" Height="30" Click="Button_Click" DockPanel.Dock="Top"/&gt; &lt;DataGrid ItemsSource="{Binding Path=People}" AutoGenerateColumns="False" SelectionUnit="CellOrRowHeader" RowDetailsVisibilityMode="Visible"&gt; &lt;DataGrid.Columns&gt; &lt;DataGridTextColumn Header="Salary" Binding="{Binding Path=Salary,StringFormat='{}{0:#,0}'}"/&gt; &lt;DataGridTextColumn Header="Name" Binding="{Binding Path=Name}"/&gt; &lt;DataGridCheckBoxColumn Header="IsLocked" Binding="{Binding Path=IsLocked,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"/&gt; &lt;/DataGrid.Columns&gt; &lt;DataGrid.RowDetailsTemplate&gt; &lt;DataTemplate&gt; &lt;DataGrid ItemsSource="{Binding Path=Kids}" AutoGenerateColumns="False" IsReadOnly="{Binding Path=IsLocked}" SelectionUnit="CellOrRowHeader"&gt; &lt;DataGrid.Columns&gt; &lt;DataGridTextColumn Header="Id" Binding="{Binding Path=Id,StringFormat='{}{0:#,0}'}"/&gt; &lt;DataGridTextColumn Header="Name" Binding="{Binding Path=Name}"/&gt; &lt;/DataGrid.Columns&gt; &lt;/DataGrid&gt; &lt;/DataTemplate&gt; &lt;/DataGrid.RowDetailsTemplate&gt; &lt;/DataGrid&gt; &lt;/DockPanel&gt; </code></pre> <p></p>
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    1. COTab out will invoke the DG's internal end-of-edit method. If you do not tab out, but click with your mouse in another row, does the same behaviour occur?
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      1. USGayot Fow
    2. CO@GarryVass. You are right. The exception only occurs upon pressing tab not upon mouse usage.
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    3. COAlso the internal transaction control on a DG will override your OnPropertyChanged to make it Explicit.
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A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

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