Alternative To Multiple using Blocks

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In all the examples I see for Entity Framework data access, every method has its own using block, as shown below.

Is there an alternative to this approach? For example, can the context object just be a class member, such as:

MyModelContext context = new MyModelContext();

Is there a reason why a new context object has to be created for each method in the DAO class?

public class DaoClass
{
    public void DoSomething()
    {
         using (var context = new MyModelContext()) 
         {     
             // Perform data access using the context 
         }
    }

    public void DoAnotherThing()
    {
         using (var context = new MyModelContext()) 
         {     
             // Perform data access using the context 
         }
    }

    public void DoSomethingElse()
    {
         using (var context = new MyModelContext()) 
         {     
             // Perform data access using the context 
         }
    }

}

You could have the DaoClass implement IDisposable and have the context be a property of the class. Just make sure to wrap DaoClass in a using statement or call Dispose() on the instance of the DaoClass.

public class DaoClass : IDisposable
{
    MyModelContext context = new MyModelContext();

    public void DoSomething()
    {
        // use the context here
    }

    public void DoAnotherThing()
    {
        // use the context here
    }

    public void DoSomethingElse()
    {
        // use the context here
    }

    public void Dispose()
    {
        context.Dispose();
    }
}

C# Language, c# documentation: Multiple using statements with one block. An alternative is to write: using (var input = File.OpenRead("input.txt")) using (var output = File. When you insert a block, AutoCAD looks to see if that block already exists in the current file. If it does, then the software will use the block that is in the file. This is a good thing, as it keeps you from messing up blocks in your file that you have customized.

Please note that the context object is the equivalent to a database transaction.

It implements the IDisposable interface because a transaction must be closed when done with and you either have to use the using statement or make an implementation of IDisposable like Lews Therin demonstrated.

We use multiple instances of a context object to separate different transactions. There will be cases when you want all changes to go as a single transaction and either commit all together or rollback everything. Then you put it all in one context instance. But there will also be cases where you want to separate the saving of one data pack from another. Then you use different transactions, i.e. different context objects.

To get a better grasp of this chapter take a look at the unit of work pattern.

Hope I could help, merry coding!

using statement, Beginning with C# 8.0, you can use the following alternative syntax Within the using block, the object is read-only and can't be modified Notice that you can't use implicitly typed variables ( var ) when you declare multiple  The try block opens where the variable is declared. The finally block is added at the close of the enclosing block, typically at the end of a method. For more information about the try-finally statement, see the try-finally article. Multiple instances of a type can be declared in a single using statement, as

The way you show it is how I've seen it recommended everywhere. I've seen there be weird issues with class level declaration returning stale or incorrect data.

To get around duplicating all the code I like to write an execute method that I can reuse, or make changes without having to go to every using.

   private T Execute<T>(Func<MyModelContext, T> function)
        {
            using (MyModelContext ctx = new MyModelContext())
            {
                var result = function(ctx);
                ctx.SaveChanges();
                return result;
            }
        }

  public List<Type> GetTypes()
        {
            return Execute((ctx) =>
            {
                return ctx.Types.ToList();
            });
        }

Draft Environmental Impact Statement: Boise National Forest, helped assure that a broad range of alternatives was considered, since several when formulating management prescriptions, the building blocks of alternatives. Each management prescription ensures "multiple-use" management, and  For objects that implement IDisposable, a using block is the best way to assure that you call Dispose on them when you are done, and the scoping prevents accidental use after disposal. In that way, your code is fine.

Building Product Models: Computer Environments, Supporting Design , Some are predefined and others can be defined for use by applications. The geometric description is held together with a Block to make the total solid model. There are several, alternative ways to partially represent the multiple-view wall​  Using the Decision Between Multiple Alternatives Process Type, check whether the flag for a particular process chain is checked or no. If it is checked, then execute Step 1, else execute Step 2. 2. Steps to create a Custom Function. 1. Using SE19 create a new implementation of BAdI RSAR_CONNECTOR: 2. Enter the Implementation Name: 3.

Using Statement, Declares the beginning of a Using block and optionally acquires the have already acquired the resource, use the second syntax alternative. These blocks are used in electrical power distribution. An electric power distribution terminal block is a convenient, economical and safer way to distribute power from a single input source to multiple outputs. One large wire is connected to the input terminal of the block and multiple output terminals are provided at the output.

Why I prefer objects over switch statements, love to use a switch statement or a huge if with multiple else if conditions. one, it then finds the break keyword in the third case block and stops the If we had a similar function that returns another functions but without  Look for instance into the generated assembly code (use gcc -O2 -fverbose-asm -S to get it) or look into the internal representations, e.g. using the the MELT probe (or passing -fdump-tree-all-giving many dump files to you- to gcc). With GCC extensions, for your specific example, you could even code case ranges like this: switch (c) { case 'A'

Comments
  • You could push the responsibility to dispose up to the consumer by instantiating the context as a field during construction, implementing IDisposable on the DaoClass, and making sure all consumers are properly disposing of it. In your current case, each method is responsible for provisioning and disposing of it's resources.
  • So is the only benefit of the using statements in my original post is the disposal of the object? Is that correct?
  • Correct. using statements are just syntactic sugar. It wraps the statement in the parenthesis in a try...finally block and calls the object's Dispose() method in the finally block. See this answer.
  • Note that while a DbContext instance is intended to support a UnitOfWork, it is a bigger scope than a database transaction. You might fetch data, work on it in memory and finally save it to the database in your UnitOfWork. This would be too long-running for a database transaction. I might be better to describe the scope as a "business transaction".