When Should I Dispose of Data Contexts in LINQ to SQL?

When Should Data Contexts Be Disposed?

In data access layers that utilize LINQ classes, it's common to encounter the question of managing data contexts. Let's consider the following code snippet:

private DataContext myDb;
public static MyClass GetMyClassById(int id)
{
    DataContext db = new DataContext();
    MyClass result = (from item in db.MyClasss
                      where item.id == id
                      select item).Single();
    result.myDb = db;
    return result;
}

public void Save()
{
    db.SubmitChanges();
}

This pattern raises questions about instantiating data contexts and the necessity of disposing them. To address this, we consulted Matt Warren of the LINQ to SQL team for guidance.

According to Warren, implementing IDisposable serves several purposes:

• Enforcing contract: IDisposable allows enforcement of the contract that entities can only be held onto beyond the expected use of the DataContext if Dispose is called.
• Clearing cache: Dispose forces the DataContext to clear its cache of materialized entities, preventing unintentional preservation of all entities through a single cached entity.
• Closing connections: While the DataContext automatically closes connections, certain circumstances can interfere with this process. Dispose provides a workaround in such cases.

Warren emphasized that in most cases, disposing DataContexts is not strictly necessary. However, for consistency and clarity, it's often preferable to dispose of any objects implementing IDisposable.

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