Automatic update of data grid when table changes

Question

Don't throw stones at me - I am quite new in programming.

The main question is how to automatically update datagrid, which represents SQL table by means of Enity Framework, after every change in this table?

I create a simple application with WPF for working with SQL tables by means of Entity Framework 6. There is image a part of this application :

So there is datagrid, that looks like this:

<DataGrid CanUserAddRows="False" AutoGenerateColumns="False" x:Name="variableAssignmentDataGrid" ItemsSource="{Binding VariableAssignment,UpdateSourceTrigger=PropertyChanged}" Margin="30" >
    <DataGrid.Columns>
        <DataGridTextColumn Width="1*" Binding="{Binding Id}" Header="Id" IsReadOnly="True"  />
        <DataGridTextColumn Width="1*" Binding="{Binding IdMachine}" Header="IdMachine"/>
        <DataGridTextColumn Width="1*" Binding="{Binding IdVariable}" Header="IdVariable"/>
        <DataGridTextColumn Width="1*" Binding="{Binding IdUser}" Header="Id User"/>
        <DataGridTextColumn Width="1*" Binding="{Binding Variable.Name}" Header="Name"/>
        <DataGridTextColumn Width="1*" Binding="{Binding Subscription}" Header="Subscription"/>
        <DataGridTextColumn Width="1*" Binding="{Binding Frequency}" Header="Frequency"/>
        <DataGridCheckBoxColumn Width="1*" Binding="{Binding Enable,Mode=TwoWay}" Header="Enable"/>
        <DataGridTextColumn Width="1.75*" Binding="{Binding Time}" Header="Time" FontSize="8"/>
        <DataGridTemplateColumn Width="1*" Header="Modify" />
    </DataGrid.Columns>
</DataGrid>

VariableAssignment, which is used for binding looks like this:

public class DataManager : INotifyPropertyChanged
{
    public Entities context = new Entities();
    private ObservableCollection<VariableAssignment> variableAssignment;
    public ObservableCollection<VariableAssignment> VariableAssignment
    {
        get { return variableAssignment; }
        set { variableAssignment = value; OnPropertyChanged("VariableAssignment"); }
    }
  ..}

In constructor of this class I fill this VariableAssignment by elements from SQL table (context.VariableAssignments)

public DataManager()
{
    VariableAssignment = new ObservableCollection<VariableAssignment>(context.VariableAssignments);
    newVariableAssignment = new VariableAssignment();
}

As you can see, in this constructor I defined newVariableAssignment = new VariableAssignment(); - I need this for adding new rows in my SQL tables.

Adding method is here

public void addNewVariableAssignment(..)
{
    context.VariableAssignments.Add(newVariableAssignment); 


    newVariableAssignment.IdVariable = //adding values

    context.SaveChanges(); 
}

This method is worked after clicking on add button.

private void addVariableButton_Click(object sender, RoutedEventArgs e)
{
    dataManager.addNewVariable(..);
}

After clicking on ADD button - Row is added to SQL table, but my datagrid doesn't update. As you see, I tried UpdateSourceTrigger, but for some reason it doesn't work. I found the only way, that updates my datagrid - create new ObservableCollection of my Table and put it into ItemsSource of datagrid after clicking button (See below)

private void addVariableButton_Click(object sender, RoutedEventArgs e)
{
    dataManager.addNewVariable(addNameVariableTextBox.Text, addAddressTexBox.Text, addVariableTypeComboBox.Text, addSourceTypeAddComboBox.Text);

    var varAssignSource = new ObservableCollection<VariableAssignment>(dataManager.context.VariableAssignments);
    variableAssignmentDataGrid.ItemsSource = varAssignSource;
}

But it isn't right, right? I mean... Now for updating the datagrid I need to write code manually in some methods/buttons/everything, that changes my table. But I want a datagrid to update automatically after changing from anywhere.

So can you give me some advices?

Answer 1

add Assignment object not only to db context, but also to ObservableCollection at the same time.

public void addNewVariableAssignment()
{
    newVariableAssignment = new VariableAssignment();
    newVariableAssignment.IdVariable = //adding values

    context.VariableAssignments.Add(newVariableAssignment); 

    context.SaveChanges(); 

    VariableAssignments.Add(newVariableAssignment);
}

DataGrid will be notified about new items added, because ObservableCollection implements INotifyCollectionChanged. There is no need to reset ItemsSource repeatedly