Serialize Expression to access string

Question

I'm working on something similar to a text templating engine.
I'm providing metadata from my server to the client to represent an javascript version of the access path for instance:

Say I have a DTO:

public class Employee
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

I have a mapping on the server which looks like so:

Expression<Func<Employee, string>> firstNameExpression = e => employee.FirstName;

When returned to the client I would like to return something similar a string representation of the expression

$"{nameof(Employee)}.{nameof(Employee.FirstName)}";

I would prefer not to have to parse the expression manually or walk the expression tree.

//e.g Pseudo Code

LambdaExpression expression
if(expression is MemberExpression expr)
{
   stringBuilder.Prepend(expr.Body.Member.Name)
}
//... Handle errors

Is there a simple way to output and expression as if it were written in code in some way?

user20416 · Accepted Answer · 2021-06-03 05:51:54Z

1

If you need to precisely serialize/deserialize the expression tree, Serialize.Linq library might help.

If all you want is some kind of string representation for display purposes, then I would recommend the ExpressionTreeToString library that I've written:

using ExpressionTreeToString;

Console.WriteLine(firstNameExpression.ToString("C#"));
/*
    e => e.FirstName
*/

Console.WriteLine(firstNameExpression.ToString("Textual tree", "C#"));
/*
    Lambda (Func<Employee, string>)
        · Parameters[0] - Parameter (Employee) e
        · Body - MemberAccess (string) FirstName
            · Expression - Parameter (Employee) e
*/

There are various string representations available.

(Disclaimer: I am the author of the latter library.)

answered Jun 3, 2021 at 5:51

user20416

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1 Comment

johnny 5 Over a year ago

I ended up working around the original problem, but this library looks like it would solve my problem

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