Hi everybody,

I need to create a library project what we should be able to use from VFP project and C# project (and, potentially although unlikely from C++).

There is another solution here by another developer - quite complex for me. I'm trying to use it as a prototype for my project.

That solution consists of many projects. One of them has the following file in the project

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

namespace DllExport
{
    /// <summary>
    /// Attribute added to a static C# method to export it
    /// </summary>
    [AttributeUsage(AttributeTargets.Method)]
    public class DllExportAttribute : Attribute
    {
        private string m_exportName;
        private CallingConvention m_callingConvention;

        /// <summary>
        /// Constructor 1
        /// </summary>
        /// <param name="exportName"></param>
        public DllExportAttribute(string exportName)
            : this(exportName, System.Runtime.InteropServices.CallingConvention.StdCall)
        {
        }

        /// <summary>
        /// Constructor 2
        /// </summary>
        /// <param name="exportName"></param>
        /// <param name="callingConvention"></param>
        public DllExportAttribute(string exportName, CallingConvention callingConvention)
        {
            m_exportName = exportName;
            m_callingConvention = callingConvention;
        }

        /// <summary>
        /// Get the export name, or null to use the method name
        /// </summary>
        public string ExportName
        {
            get { return m_exportName; }
        }

        /// <summary>
        /// Get the calling convention
        /// </summary>
        public string CallingConvention
        {
            get
            {
                switch (m_callingConvention)
                {
                    case System.Runtime.InteropServices.CallingConvention.Cdecl:
                        return typeof(CallConvCdecl).FullName;

                    case System.Runtime.InteropServices.CallingConvention.FastCall:
                        return typeof(CallConvFastcall).FullName;

                    case System.Runtime.InteropServices.CallingConvention.StdCall:
                        return typeof(CallConvStdcall).FullName;

                    case System.Runtime.InteropServices.CallingConvention.ThisCall:
                        return typeof(CallConvThiscall).FullName;

                    case System.Runtime.InteropServices.CallingConvention.Winapi:
                        return typeof(CallConvStdcall).FullName;

                    default:
                        return "";
                }
            }
        }
    }
}

and the other class in that project uses that attribute this way

[DllExport("Test", System.Runtime.InteropServices.CallingConvention.StdCall)]
        public static String Test(String dataSource, String initialCatalog)
        {
            return dataSource + ' ' + initialCatalog;
        }

that class is static and all methods and properties are static too for that class.

Do I need to follow the same in my new project and add that attribute class as well?

The VFP calls are

declare integer InitializeConnection in "Siriusware.Fingerprint.Netlink x86.dll" string, string
					lnInitializeCode = InitializeConnection(.cODBC_DSN, .cDatabase)

Just want to understand if this is needed in my case too?

My class is supposed to use HttpClient class and use its post and get methods to communicate with external API. I found this sample

https://www.dotnetperls.com/httpclient

is it how I generally should do it?

Thanks a lot in advance.