SqlConnection::BeginTransaction Method (IsolationLevel)
Starts a database transaction with the specified isolation level.
Assembly: System.Data (in System.Data.dll)
Parameters
- iso
-
Type:
System.Data::IsolationLevel
The isolation level under which the transaction should run.
Return Value
Type: System.Data.SqlClient::SqlTransaction^An object representing the new transaction.
| Exception | Condition |
|---|---|
| SqlException | Parallel transactions are not allowed when using Multiple Active Result Sets (MARS). |
| InvalidOperationException | Parallel transactions are not supported. |
This command maps to the SQL Server implementation of BEGIN TRANSACTION.
You must explicitly commit or roll back the transaction using the Commit or Rollback method. To make sure that the .NET Framework Data Provider for SQL Server transaction management model performs correctly, avoid using other transaction management models, such as the one provided by SQL Server.
 Note |
|---|
After a transaction is committed or rolled back, the isolation level of the transaction persists for all subsequent commands that are in autocommit mode (the SQL Server default). This can produce unexpected results, such as an isolation level of REPEATABLE READ persisting and locking other users out of a row. To reset the isolation level to the default (READ COMMITTED), execute the Transact-SQL SET TRANSACTION ISOLATION LEVEL READ COMMITTED statement, or call SqlConnection::BeginTransaction followed immediately by SqlTransaction::Commit. For more information on SQL Server isolation levels, see "Isolation Levels in the Database Engine" in SQL Server Books Online. |
For more information on SQL Server transactions, see "Explicit Transactions" and "Coding Efficient Transactions" in SQL Server Books Online.
 Caution |
|---|
When your query returns a large amount of data and calls BeginTransaction, a SqlException is thrown because SQL Server does not allow parallel transactions when using MARS. To avoid this problem, always associate a transaction with the command, the connection, or both before any readers are open. |
The following example creates a SqlConnection and a SqlTransaction. It also demonstrates how to use the BeginTransaction, a Commit, and Rollback methods.
Available since 1.1