Extend property auto generated class by entity framework

Question

I have a WPF application, in which I use Entity Framework .

The collection that is bound to the DataGrid is a collection of auto generated classes of the table generated by Entity Framework .

Model

(auto-generated by Entity Framework)

public partial class tblTest
{
    public tblTest()
    {
    }

    public int TestId{get;set;}
    public string TestName {get;set;}
    public string UpdatedBy {get;set;}
}

ViewModel

private ObservableCollection<tblTest> _objTest; 

public ObservableCollection<tblTest> TestList
{
     get { return _objTest; }
     set { _objTest; = value;}
}

XAML

<DataGrid Name="grdTest" ItemSource="{Binding Path=TestList,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}
AutoGenerateColumns="False" CanUserAddRows="True">
    <Datagrid.Columns>
    <DataGridTextColumn Width="140">
        <DataGridTextColumn.Binding>
            <Binding Path="TestName" Mode="TwoWay" >
                <Binding.ValidationRules>
                    <localVal:ValidationRules/>
                </Binding.ValidationRules>                           
            </Binding>
        </DataGridTextColumn.Binding>                                        
        <DataGridTextColumn.Header>
            <TextBlock Width="128" Text="Test Name" ToolTip="Enter name"/>
        </DataGridTextColumn.Header>
    </DataGridTextColumn>

    <DataGridTextColumn Width="140">
        <DataGridTextColumn.Binding>
            <Binding Path="UpdatedBy" Mode="TwoWay" >
                <Binding.ValidationRules>
                    <localVal:ValidationRules/>
                </Binding.ValidationRules>                           
            </Binding>
        </DataGridTextColumn.Binding>                                        
        <DataGridTextColumn.Header>
            <TextBlock Width="128" Text="Updated By" ToolTip="Name of the user that updated the record"/>
        </DataGridTextColumn.Header>
    </DataGridTextColumn>
    </Datagrid.Columns>
</DataGrid>

I allow the user to add new rows in the DataGrid , when a new empty row is added in the DataGrid I want the UpdatedBy column to be auto generated by the current user credentials (and it is made readonly ).

Is there a way to extend the model class of the test table to write a constructor to take current user details as updated by. Or is there a different approach for this?

Answer 1

Yes you can do this by adding a new part to the auto-generated class, typically in a new file:

public partial class tblTest
{
    public tblTest(string updatedBy)
    {
        this.UpdatedBy = updatedBy;
    }
}

The secret is the partial keyword that instructs the compiler that the whole class can be split into more than one source file.

---

EDIT: you can handle the AddingNewItem event to do what you want:

In the XAML:

<DataGrid ... AddingNewItem="DataGrid_AddingNewItem" ...>
...
<DataGridTextColumn Width="140" IsReadOnly="True">

In the code behind:

private void DataGrid_AddingNewItem(object sender, AddingNewItemEventArgs e)
{
    e.NewItem = new tblTest { UpdatedBy = Environment.UserName };
}

It will be triggered each time the user is willing to add a new item, by entering edit mode of the last empty row.