Added class RegistrationEntry.

Author: Sergey-Vlasov

Source/ExcelDna.Integration/Registration/Attributes.cs

@@ -18,4 +18,17 @@ public ExcelAsyncFunctionAttribute()
             ExplicitRegistration = true;
         }
     }
+
+    // Internal marker attribute when we process a params function.
+    // Need to keep track of the params even after we wrap the function in a lambda expression.
+    class ExcelParamsArgumentAttribute : ExcelArgumentAttribute
+    {
+        public ExcelParamsArgumentAttribute(ExcelArgumentAttribute original)
+        {
+            // Just copy all the fields
+            AllowReference = original.AllowReference;
+            Description = original.Description;
+            Name = original.Name;
+        }
+    }
 }

Source/ExcelDna.Integration/Registration/RegistrationEntry.cs

@@ -0,0 +1,56 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Linq.Expressions;
+using System.Reflection;
+using ExcelDna.Integration;
+
+namespace ExcelDna.CustomRegistration
+{
+    public class RegistrationEntry
+    {
+        public LambdaExpression FunctionLambda { get; set; }                     // Function which will be registered, and invoked by Excel
+        public ExcelFunctionAttribute FunctionAttribute { get; set; }            // ExcelFunctionAttribute which is registered with Excel. Must not be null
+        public List<ExcelArgumentAttribute> ArgumentAttributes { get; set; }     // A list of ExcelArgumentAttributes with length equal to the number of parameters in Delegate
+        public MethodInfo MethodInfo { get; private set; }                       // The method this entry was originally constructed with (may be useful for transformations).
+
+        // NOTE: 16 parameter max for Expression.GetDelegateType
+        public RegistrationEntry(MethodInfo methodInfo)
+        {
+            MethodInfo = methodInfo;
+
+            var paramExprs = methodInfo.GetParameters()
+                             .Select(pi => Expression.Parameter(pi.ParameterType, pi.Name))
+                             .ToArray();
+            FunctionLambda = Expression.Lambda(Expression.Call(methodInfo, paramExprs), methodInfo.Name, paramExprs);
+
+            // Need to make sure we have explicit 
+            FunctionAttribute = methodInfo.GetCustomAttribute<ExcelFunctionAttribute>();
+            if (FunctionAttribute == null)
+                FunctionAttribute = new ExcelFunctionAttribute { Name = methodInfo.Name };
+            else if (string.IsNullOrEmpty(FunctionAttribute.Name))
+                FunctionAttribute.Name = methodInfo.Name;
+
+            ArgumentAttributes = new List<ExcelArgumentAttribute>();
+            foreach (var pi in methodInfo.GetParameters())
+            {
+                var argAtt = pi.GetCustomAttribute<ExcelArgumentAttribute>();
+                if (argAtt == null)
+                    argAtt = new ExcelArgumentAttribute { Name = pi.Name };
+                else if (string.IsNullOrEmpty(argAtt.Name))
+                    argAtt.Name = pi.Name;
+
+                ArgumentAttributes.Add(argAtt);
+            }
+
+            // Special check for final Params argument - transform to an ExcelParamsArgumentAttribute
+            // NOTE: This won't work with a custom derived attribute...
+            var lastParam = methodInfo.GetParameters().LastOrDefault();
+            if (lastParam != null && lastParam.GetCustomAttribute<ParamArrayAttribute>() != null)
+            {
+                var excelParamsAtt = new Registration.ExcelParamsArgumentAttribute(ArgumentAttributes.Last());
+                ArgumentAttributes[ArgumentAttributes.Count - 1] = excelParamsAtt;
+            }
+        }
+    }
+}