Add project files.

src/modules/Elsa.CSharp/Contracts/ICSharpEvaluator.cs

@@ -0,0 +1,32 @@
+using Elsa.Expressions.Models;
+using JetBrains.Annotations;
+using Microsoft.CodeAnalysis.Scripting;
+
+namespace Elsa.CSharp.Contracts;
+
+/// <summary>
+/// Evaluates C# expressions.
+/// </summary>
+[PublicAPI]
+public interface ICSharpEvaluator
+{
+    /// <summary>
+    /// Evaluates a C# expression.
+    /// </summary>
+    /// <param name="expression">The expression to evaluate.</param>
+    /// <param name="returnType">The type of the return value.</param>
+    /// <param name="context">The context in which the expression is evaluated.</param>
+    /// <param name="options">A set of options.</param>
+    /// <param name="configureScriptOptions">An optional callback to configure the script options.</param>
+    /// <param name="configureScript">An optional callback to configure the script.</param>
+    /// <param name="cancellationToken">An optional cancellation token.</param>
+    /// <returns>The result of the evaluation.</returns>
+    Task<object?> EvaluateAsync(
+        string expression, 
+        Type returnType, 
+        ExpressionExecutionContext context,
+        ExpressionEvaluatorOptions options,
+        Func<ScriptOptions, ScriptOptions>? configureScriptOptions = default,
+        Func<Script<object>, Script<object>>? configureScript = default,
+        CancellationToken cancellationToken = default);
+}