Why do we need to use Unit of Work when using EF?

There can be a debate on this, i have seen developers with 10-12 years of experience.

They include update and save in their Repository class which i personally think is violation of the exact meaning of Repository.
what does a repository actually mean? A repository is only a collection of domain objects, now tell me have you ever seen below code

var list = new List<int>();
list.Save(); // doesn't exist!
list.Update(); // doesn't exist!

3. What you see is

list.Add(1);
list.Remove(1);
list.Find(1);

4. Clearly , Save and Update is not a part of Collection, so your Repository should not Contain Save and Update.

Yes , DbSet is a Generic Repository that is the reason you only see Add, AddRange,Remove and Find methods on this, you will never see Save or Update on DbSet.

Then , Where to keep Save and Update method ?

This is exactly where you need UOW, to maintain database inetegrety , either all operation fail or all commit.

Yes, DbContext is UOW , that is the reason you see SaveChanges() and Entry() method here.

Then do we need UOW explicitely?

UOW is the place (class) where all your Concerete Repository resides as a get only property, and all your repository shares the comman or single instance of DbContext thus maintain database integrity.

public GenericRepository CRM_ContactRepository
{
get
{
if (this._CRM_ContactRepository == null)
this._CRM_ContactRepository = new GenericRepository(_context);
return _CRM_ContactRepository;
}
}
public GenericRepository CRM_ProductRepository
{
get
{
if (this._CRM_ProductRepository == null)
this._CRM_ProductRepository = new GenericRepository(_context);
return _CRM_ProductRepository;
}
}

As you can see both Repository shares the same instance of DbContext.

2 Replies

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Sachin Singh6y ago
Accepted answer
There can be a debate on this, i have seen developers with 10-12 years of experience.
They include update and save in their Repository class which i personally think is violation of the exact meaning of Repository.
what does a repository actually mean? A repository is only a collection of domain objects, now tell me have you ever seen below code
var list = new List<int>();
list.Save();    // doesn't exist!
list.Update();  // doesn't exist!
   3. What you see is
list.Add(1);
list.Remove(1);
list.Find(1);
4. Clearly , Save and Update is not a part of Collection, so your Repository should not Contain Save and Update.

Yes , DbSet is a Generic Repository that is the reason you only see Add, AddRange,Remove and Find methods on this, you will never see Save or Update on DbSet.

Then , Where to keep Save and Update method ?
This is exactly where you need UOW, to maintain database inetegrety , either all operation fail or all commit.
Yes, DbContext is UOW , that is the reason you see SaveChanges() and Entry() method here.

Then do we need UOW explicitely?
UOW is the place (class) where all your Concerete Repository resides as a get only property, and all your repository shares the comman or single instance of DbContext thus maintain database integrity.
public GenericRepository CRM_ContactRepository
       {
           get
           {


               if (this._CRM_ContactRepository == null)
                   this._CRM_ContactRepository = new GenericRepository(_context);
               return _CRM_ContactRepository;
           }
       }
       public GenericRepository CRM_ProductRepository
       {
           get
           {


               if (this._CRM_ProductRepository == null)
                   this._CRM_ProductRepository = new GenericRepository(_context);
               return _CRM_ProductRepository;
           }
       }
As you can see both Repository shares the same instance of DbContext.
+1
Nisha Regil6y ago
May be this can be helpful to understand.
https://gunnarpeipman.com/ef-core-repository-unit-of-work/
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