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How to: Create and Run a SQL Server Trigger by using Common Language Run-time Integration

Create a SQL trigger by adding a Trigger item to a SQL Server Common Language Run-time (SQL CLR) database project. After successful deployment, triggers that are created in managed code are called and executed like any other Transact-SQL trigger. Triggers that are written in a managed language can use the SqlTriggerContext class to obtain access to the same information that is available to Transact-SQL triggers.

NoteNote

Your computer might show different names or locations for some of the Visual Studio user interface elements in the following instructions. The Visual Studio edition that you have and the settings that you use determine these elements. For more information, see Visual Studio Settings.

To create a SQL Server Trigger

  1. Open an existing SQL CLR Database Project, or create a new one. For more information, see How to: Create a Project for Database Objects that Use SQL Server Common Language Run-time Integration.

  2. On the Project menu, select Add New Item.

  3. In the Add New Item dialog box, select Trigger.

  4. Type a Name for the new trigger.

  5. Add code to run when the trigger is executed. See the first example that follows this procedure.

  6. In Solution Explorer, open the TestScripts folder and double-click the Test.sql file.

    NoteNote

    You can specify other scripts as your default debug script. For more information, see How to: Edit the Test.sql Script to Run Objects that use SQL Server Common Language Run-time Integration.

  7. Add code to the Test.sql file to execute the trigger. See the second example that follows this procedure.

  8. Press F5 to build, deploy, and debug the trigger. For information about how to deploy without debugging, see How to: Deploy SQL Server CLR Integration Database Project Items to a SQL Server.

    Important noteImportant

    SQL Server 2005 and SQL Server 2008 only support SQL Server projects that were built with the 2.0, 3.0, or 3.5 version of the .NET Framework. If you try to deploy a SQL Server project to SQL Server 2005 or SQL Server 2008, an error appears: Deploy error (SQL01268): .NET SqlClient Data Provider: Msg 6218, Level 16, State 3, Line 1 CREATE ASSEMBLY for assembly 'AssemblyName' failed because assembly 'AssemblyName' failed verification. Check if the referenced assemblies are up-to-date and trusted (for external_access or unsafe) to execute in the database (where AssemblyName is the name of the assembly that you are deploying). For more information, see How to: Create a Project for Database Objects that Use SQL Server Common Language Run-time Integration.

  9. View the results that are shown in the Output Window and select Show output from: Database Output.

This example demonstrates the scenario where the users choose any user name they want, but you want to know which users entered an e-mail address as a user name. This trigger detects that information and logs it to an audit table.


using System.Data.SqlClient;
using System.Text.RegularExpressions;
using Microsoft.SqlServer.Server;

public partial class Triggers
{
    [SqlTrigger(Name="UserNameAudit", Target="Users", Event="FOR INSERT")]
    public static void UserNameAudit()
    {
        SqlTriggerContext triggContext = SqlContext.TriggerContext;
        SqlParameter userName = new SqlParameter("@username", System.Data.SqlDbType.NVarChar);

        if (triggContext.TriggerAction == TriggerAction.Insert)
        {
            using (SqlConnection conn = new SqlConnection("context connection=true"))
            {
                conn.Open();
                SqlCommand sqlComm = new SqlCommand();
                SqlPipe sqlP = SqlContext.Pipe;

                sqlComm.Connection = conn;
                sqlComm.CommandText = "SELECT UserName from INSERTED";

                userName.Value = sqlComm.ExecuteScalar().ToString();

                if (IsEMailAddress(userName.ToString()))
                {
                    sqlComm.CommandText = "INSERT UsersAudit(UserName) VALUES(userName)";
                    sqlP.Send(sqlComm.CommandText);
                    sqlP.ExecuteAndSend(sqlComm);
                }
            }
        }
    }


    public static bool IsEMailAddress(string s)
    {
        return Regex.IsMatch(s, "^([\\w-]+\\.)*?[\\w-]+@[\\w-]+\\.([\\w-]+\\.)*?[\\w]+$");
    }
}


Add code to execute and test your trigger to the Test.sql file in the TestScripts folder in your project. For example, if you deployed a trigger, you can test it by running a script that inserts a new row into the table on which the trigger is set causing the trigger to fire. The following debugging code assumes that two tables exist with the following definitions:

CREATE TABLE Users
(
    UserName    NVARCHAR(200)    NOT NULL,
    Pass    NVARCHAR(200)    NOT NULL
)

CREATE TABLE UsersAudit
(
    UserName    NVARCHAR(200)    NOT NULL
)
-- Insert one user name that is not an e-mail address and one that is
INSERT INTO Users(UserName, Pass) VALUES(N'someone', N'cnffjbeq')
INSERT INTO Users(UserName, Pass) VALUES(N'someone@example.com', N'cnffjbeq')

-- check the Users and UsersAudit tables to see the results of the trigger
select * from Users
select * from UsersAudit

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