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title description author ms.author ms.reviewer ms.date ms.service ms.subservice ms.topic
Local transactions
Demonstrates how to perform transactions against a database with Microsoft SqlClient Data Provider for SQL Server.
David-Engel
v-davidengel
v-chmalh
11/24/2020
sql
connectivity
conceptual

Local transactions

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Transactions in ADO.NET are used when you want to bind multiple tasks together so that they execute as a single unit of work. For example, imagine that an application performs two tasks. First, it updates a table with order information. Second, it updates a table that contains inventory information, debiting the items ordered. If either task fails, then both updates are rolled back.

Determining the transaction type

A transaction is considered to be a local transaction when it is a single-phase transaction and is handled by the database directly. A transaction is considered to be a distributed transaction when it is coordinated by a transaction monitor and uses fail-safe mechanisms (such as two-phase commit) for transaction resolution.

The Microsoft SqlClient Data Provider for SQL Server has its own xref:Microsoft.Data.SqlClient.SqlTransaction object for performing local transactions in SQL Server databases. Other .NET data providers also provide their own Transaction objects. In addition, there is a xref:System.Data.Common.DbTransaction class that is available for writing provider-independent code that requires transactions.

Note

Transactions are most efficient when they are performed on the server. If you are working with a SQL Server database that makes extensive use of explicit transactions, consider writing them as stored procedures using the Transact-SQL BEGIN TRANSACTION statement.

Performing a transaction using a single connection

In ADO.NET, you control transactions with the Connection object. You can initiate a local transaction with the BeginTransaction method. Once you have begun a transaction, you can enlist a command in that transaction with the Transaction property of a Command object. You can then commit or roll back modifications made at the data source based on the success or failure of the components of the transaction.

Note

The EnlistDistributedTransaction method should not be used for a local transaction.

The scope of the transaction is limited to the connection. The following example performs an explicit transaction that consists of two separate commands in the try block. The commands execute INSERT statements against the Production.ScrapReason table in the AdventureWorks SQL Server sample database, which are committed if no exceptions are thrown. The code in the catch block rolls back the transaction if an exception is thrown. If the transaction is aborted or the connection is closed before the transaction has completed, it is automatically rolled back.

Example

Follow these steps to perform a transaction.

  1. Call the xref:Microsoft.Data.SqlClient.SqlConnection.BeginTransaction%2A method of the xref:Microsoft.Data.SqlClient.SqlConnection object to mark the start of the transaction. The xref:Microsoft.Data.SqlClient.SqlConnection.BeginTransaction%2A method returns a reference to the transaction. This reference is assigned to the xref:Microsoft.Data.SqlClient.SqlCommand objects that are enlisted in the transaction.

  2. Assign the Transaction object to the xref:Microsoft.Data.SqlClient.SqlCommand.Transaction%2A property of the xref:Microsoft.Data.SqlClient.SqlCommand to be executed. If a command is executed on a connection with an active transaction, and the Transaction object has not been assigned to the Transaction property of the Command object, an exception is thrown.

  3. Execute the required commands.

  4. Call the xref:Microsoft.Data.SqlClient.SqlTransaction.Commit%2A method of the xref:Microsoft.Data.SqlClient.SqlTransaction object to complete the transaction, or call the xref:Microsoft.Data.SqlClient.SqlTransaction.Rollback%2A method to end the transaction. If the connection is closed or disposed before either the xref:Microsoft.Data.SqlClient.SqlTransaction.Commit%2A or xref:Microsoft.Data.SqlClient.SqlTransaction.Rollback%2A methods have been executed, the transaction is rolled back.

The following code example demonstrates transactional logic using the Microsoft SqlClient Data Provider for SQL Server.

[!code-csharpSqlTransactionLocal#1]

See also