How can I evaluate C# code dynamically?

Question

I can do an eval("something()"); to execute the code dynamically in JavaScript. Is there a way for me to do the same thing in C#?

An example of what I am trying to do is: I have an integer variable (say i) and I have multiple properties by the names: "Property1", "Property2", "Property3", etc. Now, I want to perform some operations on the " Propertyi " property depending on the value of i.

This is really simple with Javascript. Is there any way to do this with C#?

Answer 1

Using the Roslyn scripting API (more samples here):

// add NuGet package 'Microsoft.CodeAnalysis.Scripting' using Microsoft.CodeAnalysis.CSharp.Scripting;  await CSharpScript.EvaluateAsync("System.Math.Pow(2, 4)") // returns 16 

You can also run any piece of code:

var script = await CSharpScript.RunAsync(@"                 class MyClass                 {                      public void Print() => System.Console.WriteLine(1);                 }") 

And reference the code that was generated in previous runs:

await script.ContinueWithAsync("new MyClass().Print();"); 

Answer 2

DISCLAIMER: This answer was written back in 2008. The landscape has changed drastically since then.

Look at the other answers on this page, especially the one detailing Microsoft.CodeAnalysis.CSharp.Scripting.

Rest of answer will be left as it was originally posted but is no longer accurate.

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Unfortunately, C# isn't a dynamic language like that.

What you can do, however, is to create a C# source code file, full with class and everything, and run it through the CodeDom provider for C# and compile it into an assembly, and then execute it.

This forum post on MSDN contains an answer with some example code down the page somewhat:
create a anonymous method from a string?

I would hardly say this is a very good solution, but it is possible anyway.

What kind of code are you going to expect in that string? If it is a minor subset of valid code, for instance just math expressions, it might be that other alternatives exists.

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Edit: Well, that teaches me to read the questions thoroughly first. Yes, reflection would be able to give you some help here.

If you split the string by the ; first, to get individual properties, you can use the following code to get a PropertyInfo object for a particular property for a class, and then use that object to manipulate a particular object.

String propName = "Text"; PropertyInfo pi = someObject.GetType().GetProperty(propName); pi.SetValue(someObject, "New Value", new Object[0]); 

Link: PropertyInfo.SetValue Method