如何创建实体框架 DBContext 扩展方法？

Question

I want to write an extension method on dbContextOptionsBuilder which turns on client-side evaluation warning. All our 10 db contexts will have this extension, and this way, we can toggle all with single boolean variable.

We are preparing to eventually migrate to Entity Framework Core 3, which does not allow client side evaluation.

Would this be an proper extension method?

public static DbContextOptionsBuilder ToggleClientEvaluationWarning(this DbContextOptionsBuilder dbContextOptionsBuilder, bool toggleSwitch = false)
{
    if (toggleSwitch)
    {
        return dbContextOptionsBuilder.ConfigureWarnings(warnings => warnings.Throw(RelationalEventId.QueryClientEvaluationWarning));
    }
    else
    {
        return dbContextOptionsBuilder;
    }
}

https://devblogs.microsoft.com/dotnet/announcing-ef-core-3-0-and-ef-6-3-general-availability/

How to write an extension method in DbContext class?

Answer 1

Your code is a possible solution that could be simplified.
But before you should respect possible performance issues if you would perform more than enable client warnings.

1st simplification:

public static DbContextOptionsBuilder ToggleClientEvaluationWarning(this DbContextOptionsBuilder dbContextOptionsBuilder, bool toggleSwitch = false)
{
    if (toggleSwitch)
    {
        return dbContextOptionsBuilder.ConfigureWarnings(warnings => warnings.Throw(RelationalEventId.QueryClientEvaluationWarning));
    }

    return dbContextOptionsBuilder;
}

2nd round:

public static DbContextOptionsBuilder ToggleClientEvaluationWarning(this DbContextOptionsBuilder dbContextOptionsBuilder, bool toggleSwitch = false)
{
    return toggleSwitch
        ? dbContextOptionsBuilder.ConfigureWarnings(warnings => warnings.Throw(RelationalEventId.QueryClientEvaluationWarning))
        : dbContextOptionsBuilder;
}

Here is an additional blog post for further information.