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Walkthrough: Save data in a transaction in .NET Framework applications

  • Artikkeli

Note

Datasets and related classes are legacy .NET Framework technologies from the early 2000s that enable applications to work with data in memory while the applications are disconnected from the database. The technologies are especially useful for applications that enable users to modify data and persist the changes back to the database. Although datasets have proven to be a very successful technology, we recommend that new .NET applications use Entity Framework Core. Entity Framework provides a more natural way to work with tabular data as object models, and it has a simpler programming interface.

This walkthrough demonstrates how to save data in a transaction by using the System.Transactions namespace. In this walkthrough, you'll create a Windows Forms application. You'll use the Data Source Configuration Wizard to create a dataset for two tables in the Northwind sample database. You'll add data bound controls to a Windows form, and you'll modify the code for the BindingNavigator's save button to update the database inside a TransactionScope.

Prerequisites

To complete this tutorial, you need the .NET desktop development and Data storage and processing workloads installed in Visual Studio. To install them, open Visual Studio Installer and choose Modify (or More > Modify) next to the version of Visual Studio you want to modify. See Modify Visual Studio.

This walkthrough uses SQL Server Express LocalDB and the Northwind sample database.

  1. If you don't have SQL Server Express LocalDB, install it either from the SQL Server Express download page, or through the Visual Studio Installer. In the Visual Studio Installer, SQL Server Express LocalDB can be installed as part of the .NET desktop development workload, or as an individual component.

  2. Install the Northwind sample database by following these steps:

    1. In Visual Studio, open the SQL Server Object Explorer window. (SQL Server Object Explorer is installed as part of the Data storage and processing workload in the Visual Studio Installer.) Expand the SQL Server node. Right-click on your LocalDB instance and select New Query.

      A query editor window opens.

    2. Copy the Northwind Transact-SQL script to your clipboard. This T-SQL script creates the Northwind database from scratch and populates it with data.

    3. Paste the T-SQL script into the query editor, and then choose the Execute button.

      After a short time, the query finishes running and the Northwind database is created.

Create a Windows Forms application

The first step is to create a Windows Forms App (.NET Framework).

  1. In Visual Studio, on the File menu, select New > Project.

  2. Expand either Visual C# or Visual Basic in the left-hand pane, then select Windows Desktop.

  3. In the middle pane, select the Windows Forms App project type.

  4. Name the project SavingDataInATransactionWalkthrough, and then choose OK.

    The SavingDataInATransactionWalkthrough project is created and added to Solution Explorer.

Create a database data source

This step uses the Data Source Configuration Wizard to create a data source based on the Customers and Orders tables in the Northwind sample database.

  1. To open the Data Sources window, on the Data menu, select Show Data Sources.

  2. In the Data Sources window, select Add New Data Source to start the Data Source Configuration Wizard.

  3. On the Choose a Data Source Type screen, select Database, and then select Next.

  4. On the Choose your Data Connection screen do one of the following:

    • If a data connection to the Northwind sample database is available in the dropdown list, select it.

      -or-

    • Select New Connection to launch the Add/Modify Connection dialog box and create a connection to the Northwind database.

  5. If your database requires a password, select the option to include sensitive data, and then select Next.

  6. On the Save connection string to the Application Configuration file screen, select Next.

  7. On the Choose your Database Objects screen, expand the Tables node.

  8. Select the Customers and Orders tables, and then select Finish.

    The NorthwindDataSet is added to your project and the Customers and Orders tables appear in the Data Sources window.

Add controls to the form

You can create the data-bound controls by dragging items from the Data Sources window onto your form.

  1. In the Data Sources window, expand the Customers node.

  2. Drag the main Customers node from the Data Sources window onto Form1.

    A DataGridView control and a tool strip (BindingNavigator) for navigating records appear on the form. A NorthwindDataSet, CustomersTableAdapter, BindingSource, and BindingNavigator appear in the component tray.

  3. Drag the related Orders node (not the main Orders node, but the related child-table node below the Fax column) onto the form below the CustomersDataGridView.

    A DataGridView appears on the form. An OrdersTableAdapter and BindingSource appear in the component tray.

Add a reference to the System.Transactions assembly

Transactions use the System.Transactions namespace. A project reference to the system.transactions assembly is not added by default, so you need to manually add it.

To add a reference to the System.Transactions DLL file

  1. On the Project menu, select Add Reference.

  2. Select System.Transactions (on the .NET tab), and then select OK.

    A reference to System.Transactions is added to the project.

Modify the code in the BindingNavigator's SaveItem button

For the first table dropped onto your form, code is added by default to the click event of the save button on the BindingNavigator. You need to manually add code to update any additional tables. For this walkthrough, we refactor the existing save code out of the save button's click event handler. We also create a few more methods to provide specific update functionality based on whether the row needs to be added or deleted.

To modify the auto-generated save code

  1. Select the Save button on the CustomersBindingNavigator (the button with the floppy disk icon).

  2. Replace the CustomersBindingNavigatorSaveItem_Click method with the following code:

    private void customersBindingNavigatorSaveItem_Click(object sender, EventArgs e)
{
    UpdateData();
}

private void UpdateData()
{
    this.Validate();
    this.customersBindingSource.EndEdit();
    this.ordersBindingSource.EndEdit();

    using (System.Transactions.TransactionScope updateTransaction = 
        new System.Transactions.TransactionScope())
    {
        DeleteOrders();
        DeleteCustomers();
        AddNewCustomers();
        AddNewOrders();

        updateTransaction.Complete();
        northwindDataSet.AcceptChanges();
    }
}

The order for reconciling changes to related data is as follows:

  • Delete child records. (In this case, delete records from the Orders table.)

  • Delete parent records. (In this case, delete records from the Customers table.)

  • Insert parent records. (In this case, insert records in the Customers table.)

  • Insert child records. (In this case, insert records in the Orders table.)

To delete existing orders

  • Add the following DeleteOrders method to Form1:

    private void DeleteOrders()
{
    NorthwindDataSet.OrdersDataTable deletedOrders;
    deletedOrders = (NorthwindDataSet.OrdersDataTable)
        northwindDataSet.Orders.GetChanges(DataRowState.Deleted);

    if (deletedOrders != null)
    {
        try
        {
            ordersTableAdapter.Update(deletedOrders);
        }
        catch (System.Exception ex)
        {
            MessageBox.Show("DeleteOrders Failed");
        }
    }
}

To delete existing customers

  • Add the following DeleteCustomers method to Form1:

    private void DeleteCustomers()
{
    NorthwindDataSet.CustomersDataTable deletedCustomers;
    deletedCustomers = (NorthwindDataSet.CustomersDataTable)
        northwindDataSet.Customers.GetChanges(DataRowState.Deleted);

    if (deletedCustomers != null)
    {
        try
        {
            customersTableAdapter.Update(deletedCustomers);
        }
        catch (System.Exception ex)
        {
            MessageBox.Show("DeleteCustomers Failed");
        }
    }
}

To add new customers

  • Add the following AddNewCustomers method to Form1:

    private void AddNewCustomers()
{
    NorthwindDataSet.CustomersDataTable newCustomers;
    newCustomers = (NorthwindDataSet.CustomersDataTable)
        northwindDataSet.Customers.GetChanges(DataRowState.Added);

    if (newCustomers != null)
    {
        try
        {
            customersTableAdapter.Update(newCustomers);
        }
        catch (System.Exception ex)
        {
            MessageBox.Show("AddNewCustomers Failed");
        }
    }
}

To add new orders

  • Add the following AddNewOrders method to Form1:

    private void AddNewOrders()
{
    NorthwindDataSet.OrdersDataTable newOrders;
    newOrders = (NorthwindDataSet.OrdersDataTable)
        northwindDataSet.Orders.GetChanges(DataRowState.Added);

    if (newOrders != null)
    {
        try
        {
            ordersTableAdapter.Update(newOrders);
        }
        catch (System.Exception ex)
        {
            MessageBox.Show("AddNewOrders Failed");
        }
    }
}

Run the application

Press F5 to run the application.

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