C# Eval Expression Eval Context

The EvalContext is the main class of the C# Eval Expression library. In a few words, the EvalContext is the context under which an evaluation or compilation is executed.

You can customize the EvalContext through:

There are 3 ways to use an EvalContext:

  • Use the global EvalContext instance
  • Use a new EvalContext instance
  • Use a custom global EvalContext instance

Use the global EvalContext instance

Using the global EvalContext from the Eval Manager, is the easiest way to get started with our library.

Under the hood, methods such as Eval.Execute, Eval.Compile,String.Execute,String.Compile` and LINQ method use it by default.

The global EvalContext instance should only be customized by the options you want to apply globally. A rule of thumb is if an evaluation needs an option that cannot be set when the application starts, then this evaluation should not use the global EvalContext instance.

Use a new EvalContext instance

Creating a new EvalContext instance is often used in a method with some options that are passed in parameters such as:

Since those options cannot be set when the application starts, and they are not global but specific for this evaluation only, it makes sense to create a new context in this case.

Use a custom global EvalContext instance

Using a custom global EvalContext instance is a mixte of both previous cases. For example, let's say you already know that sometimes you need to evaluate an expression in safe mode , but you don't want these options to be in your global EvalContext instance.

Instead of re-creating the same instance again and again in every method that needs this configuration, you can create a static class with a static context already configured for this purpose:

It makes the code in your method more readable and makes it easier to change configuration globally.

Conclusion

There is no best unique way to use an EvalContext as they are all good solutions depending on your scenario. They are quite easy to learn, so make sure to understand them correctly to best use our library.


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