C# MSScriptControl Pass Class to Function

Question

I am using MSScriptControl in C#. I would like to pass a class from the script to the host. Simplified example: Javascript:

function Fx(n) {
    this.name = n;
}
var fx = new Fx("test");
rfx.DoEffect(fx);

C#:

[ComVisible(true)]
public class Rfx {
    public void DoEffect(object fx) {
        // Try to read fx.name
    }
}

My question is: How do I get the data out of the object (which C# reports as System.__ComObject). I tried the technique offered here, but it doesn't work:

public void DoEffect(object fx)
{
    System.Reflection.FieldInfo[] myFields = fx.GetType().GetFields(System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance);
    Console.WriteLine("FieldInfo length = " + myFields.Length);
    for (int i = 0; i < myFields.Length; i++)
    {
         Console.WriteLine("The value of {0} is: {1}", myFields[i].Name, myFields[i].GetValue(fx));
    }
}

myFields.Length is 0.

Instead of using System.Reflection, you'll need to get the ITypeInfo from System.Runtime.InteropServices: — Jon, Jun 26 '12 at 16:42

score 1 · Accepted Answer · answered Jun 26 '12 at 18:12

Building off Mangist's code, this works:

using System; 
using System.Runtime.InteropServices; 
using ComTypes = System.Runtime.InteropServices.ComTypes;

public class ComHelper 
{
    public static string GetValue(object comObj, string name)
    {
        if (comObj == null)
            return String.Empty;

        if (!Marshal.IsComObject(comObj))
            //The specified object is not a COM object 
            return String.Empty;

        IDispatch dispatch = comObj as IDispatch;
        if (dispatch == null)
            //The specified COM object doesn't support getting type information 
            return String.Empty; 

        try
        {
            int language_id = 0;
            int DISPATCH_METHOD = 0x1;
            int DISPATCH_PROPERTYGET = 0x2;

            int[] displayIDs = new int[1];
            Guid empty = Guid.Empty;
            string[] names = new string[] { name };
            dispatch.GetIDsOfNames(ref empty, names, names.Length, language_id, displayIDs);
            System.Runtime.InteropServices.ComTypes.DISPPARAMS dspp = new System.Runtime.InteropServices.ComTypes.DISPPARAMS();
            System.Runtime.InteropServices.ComTypes.EXCEPINFO ei = new System.Runtime.InteropServices.ComTypes.EXCEPINFO();
            IntPtr[] arg_err = new IntPtr[10];
            object result;
            if (1 == displayIDs.Length)
            {
                dispatch.Invoke(displayIDs[0], ref empty, language_id, (ushort)(DISPATCH_METHOD | DISPATCH_PROPERTYGET), ref dspp, out result, ref ei, arg_err);
                return result.ToString();
            }
            return String.Empty;
        }
        catch (Exception e)
        {
            Console.WriteLine(e.Message);
            return String.Empty;
        }
    }
}

I had done this previously in C++ so I could copy the code over, but am still getting my feet wet in C#.

RMalke · Answer 2 · 2017-10-04T14:58:36.183

1

Since the introduction of dynamic, one can treat COM Objects as dynamics, in your example you could simply do:

dynamic fx = scriptControl.Run("youFunction");
string name = fx.name;

edited Oct 04 '17 at 14:58

answered Mar 25 '15 at 14:03

RMalke

4,048
29
42

score 0 · Answer 3 · edited Mar 25 '15 at 13:51

using System; 
using System.Runtime.InteropServices; 
using ComTypes = System.Runtime.InteropServices.ComTypes; 

namespace ComUtils 
{ 
    public class ComHelper 
    { 
        /// <summary> 
        /// Returns a string value representing the type name of the specified COM object. 
        /// </summary> 
        /// <param name="comObj">A COM object the type name of which to return.</param> 
        /// <returns>A string containing the type name.</returns> 
        public static string GetTypeName(object comObj) 
        { 

            if (comObj == null) 
                return String.Empty; 

            if (!Marshal.IsComObject(comObj)) 
                //The specified object is not a COM object 
                return String.Empty; 

            IDispatch dispatch = comObj as IDispatch; 
            if (dispatch == null) 
                //The specified COM object doesn't support getting type information 
                return String.Empty; 

            ComTypes.ITypeInfo typeInfo = null; 
            try 
            { 
                try 
                { 
                    // obtain the ITypeInfo interface from the object 
                    dispatch.GetTypeInfo(0, 0, out typeInfo); 
                } 
                catch (Exception ex) 
                { 
                    //Cannot get the ITypeInfo interface for the specified COM object 
                    return String.Empty; 
                } 

                string typeName = ""; 
                string documentation, helpFile; 
                int helpContext = -1; 

                try 
                { 
                    //retrieves the documentation string for the specified type description 
                    typeInfo.GetDocumentation(-1, out typeName, out documentation, 
                        out helpContext, out helpFile); 
                } 
                catch (Exception ex) 
                { 
                    // Cannot extract ITypeInfo information 
                    return String.Empty; 
                } 
                return typeName; 
            } 
            catch (Exception ex) 
            { 
                // Unexpected error 
                return String.Empty; 
            } 
            finally 
            { 
                if (typeInfo != null) Marshal.ReleaseComObject(typeInfo); 
            } 
        } 
    } 

    /// <summary> 
    /// Exposes objects, methods and properties to programming tools and other 
    /// applications that support Automation. 
    /// </summary> 
    [ComImport()] 
    [Guid("00020400-0000-0000-C000-000000000046")] 
    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)] 
    interface IDispatch 
    { 
        [PreserveSig] 
        int GetTypeInfoCount(out int Count); 

        [PreserveSig] 
        int GetTypeInfo( 
            [MarshalAs(UnmanagedType.U4)] int iTInfo, 
            [MarshalAs(UnmanagedType.U4)] int lcid, 
            out ComTypes.ITypeInfo typeInfo); 

        [PreserveSig] 
        int GetIDsOfNames( 
            ref Guid riid, 
            [MarshalAs(UnmanagedType.LPArray, ArraySubType = UnmanagedType.LPWStr)] 
            string[] rgsNames, 
            int cNames, 
            int lcid, 
            [MarshalAs(UnmanagedType.LPArray)] int[] rgDispId); 

        [PreserveSig] 
        int Invoke( 
            int dispIdMember, 
            ref Guid riid, 
            uint lcid, 
            ushort wFlags, 
            ref ComTypes.DISPPARAMS pDispParams, 
            out object pVarResult, 
            ref ComTypes.EXCEPINFO pExcepInfo, 
            IntPtr[] pArgErr); 
    }
}

Thanks. This didn't do what I needed, but set me in the right direction. — 001, Jun 26 '12 at 18:13

C# MSScriptControl Pass Class to Function

3 Answers3