Question 1

How do I use FastExpressionCompiler in my existing .NET project?

Accepted Answer

Install the NuGet package, add 'using FastExpressionCompiler;', and replace calls to Expression.Compile() with CompileFast(). For LightExpression, change usings to FastExpressionCompiler.LightExpression.Expression and adjust code accordingly.

Question 2

Does FastExpressionCompiler work with all types of C# expressions?

Accepted Answer

No, it does not support some expression nodes like Quote, Dynamic, and DebugInfo. You can check for unsupported nodes using diagnostics or fall back to Expression.Compile() when needed.

Question 3

FastExpressionCompiler vs Expression.Compile: which should I choose?

Accepted Answer

Use FastExpressionCompiler for performance-critical applications where compilation speed and memory matter. Stick with Expression.Compile() for full compatibility or if your expressions use unsupported features.

Question 4

How can I debug an expression compiled with FastExpressionCompiler?

Accepted Answer

Pass CompilerFlags.EnableDelegateDebugInfo to CompileFast(), then use TryGetDebugInfo() to access and print the expression, C# code, and IL for detailed analysis and troubleshooting.

Question 5

What happens if FastExpressionCompiler fails to compile my expression?

Accepted Answer

By default, it returns null and falls back to Expression.Compile(), but you can configure it to throw an exception using CompilerFlags.ThrowOnNotSupportedExpression for stricter error handling.

Question 6

Can I convert between LightExpression and System.Linq.Expressions?

Accepted Answer

Yes, LightExpression provides ToExpression() to convert to System.Linq.Expressions and ToLightExpression() to convert from it, allowing interoperability with existing code and visitors.

FastExpressionCompiler

What is FastExpressionCompiler?

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