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4.3

Transactions and LINQ not playing well together

Asked by havard-fjaer in Databases Miscellaneous, Language Integrated Query - LINQ, .NET

Tags: transactions linq datacontext TransactionScope

I am having trouble with LINQ and transactions when two transactions share the same DataContext object.

In the simplified code below I will get an System.Data.SqlClient.SqlException: Violation of PRIMARY KEY constraint 'PK_User'. Cannot insert duplicate key in object 'dbo.User' when the second part of the code runs. Even though I call Dispose(); in the first code block, which should have removed the row before I start working in the second code block.

It is interesting to note that when I debug the second block with the DataContext object shared with the first block, dc.Users contain only already existing user rows; there is no trace of the user row I added in the first block of code.

Also, when I avoid DataContext and use a SqlCommand object to query the database within code block 2, there is no trace of the supposedly existing row. (It exists, of course, if I do the same query in the first code block.)

The code will work if the var dc = new WebPortalDataContext(); is created within each transaction, however in our web application we share the DataContext object for each request.  I've read several discussions on why to do this, or not -- but hope not to get into this discussion now :)

The question becomes: Why doesn't the transaction appear to roll back? 
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public void Test() 
{
    var dc = new WebPortalDataContext();
 
    // Code block 1
    using (TransactionScope trans = new TransactionScope())
    {
        dc.Users.InsertOnSubmit(new User { UserName = "testuser246", FullName = "Test User" });
        dc.SubmitChanges();
        trans.Dispose();
    } 
    
    // Code block 2 - identical to block 1
    using (TransactionScope trans = new TransactionScope())
    {
        dc.Users.InsertOnSubmit(new User { UserName = "testuser246", FullName = "Test User" });
        dc.SubmitChanges(); // This fails
        trans.Dispose();
    } 
}
 
// Testing whether the first transaction has left anything for transaction #2
DbCommand cmd = new SqlCommand("SELECT * FROM [User]");
cmd.Connection = dc.Connection; // Using the same connection as DataContext
DbDataReader reader = cmd.ExecuteReader();
[+][-]08/20/09 07:51 AM, ID: 25143251Accepted Solution

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About this solution

Zones: Databases Miscellaneous, Language Integrated Query - LINQ, .NET
Tags: transactions linq datacontext TransactionScope
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Solution Provided By: DaTribe
Participating Experts: 1
Solution Grade: B
 
[+][-]09/13/09 09:40 AM, ID: 25320855Administrative Comment

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