Ado.net Entity Framework In-depth analysis, part 6– processing concurrency (concurrency handling)

Set concurrency mode

The Entity Framework implements an optimistic concurrency pattern (optimistic concurrency model). By default, concurrency is not checked when entity update data is submitted to the database. For high frequency concurrency properties, you need to set the concurrency mode of the property to fixed.

These properties are added to the WHERE clause section of the T-SQL script to compare the client's values with the values on the database side.

Sample code:

public void UpdateProduct()
{
　Product product = context.Product.FirstOrDefault(p => p.ProductID == 1004);
　if (product != null)
　{
　　product.Color = "White";
　　product.StandardCost = 200;
　　product.ListPrice = 250;
　}
　context.SaveChanges();
}

Normally, without checking concurrency, the resulting T-SQL script is as follows:

exec sp_executesql N'update [SalesLT].[Product]
set [Color] = @0, [StandardCost] = @1, [ListPrice] = @2
where ([ProductID] = @3)',
N'@0 nvarchar(5), @1 decimal(19,4), @2 decimal(19,4), @3 int', @0=N'White', @1=1000.0000, @2=2000.0000,@3=1004

When you set the concurrency Mode for the color property of the product entity to fixed, you will find that in the generated T-SQL script, the WHERE clause adds a check to the Color field:

exec sp_executesql N'update [SalesLT].[Product]
set [Color] = @0, [StandardCost] = @1, [ListPrice] = @2
where (([ProductID] = @3) and ([Color] = @4))',
N'@0 nvarchar(5), @1 decimal(19,4), @2 decimal(19,4), @3 int, @4 nvarchar(5)', @0=N'White', @1=200.0000, @2=250.0000, @3=1004, @4=N'White'