C＃Com Interop类方法在VB6中不可见？

Question

I have created a C# Com Interop class in .NET and I have registered it appropriately on my dev machine as well as set Com-Visible to true in the assembly . However when I reference the library within my vb6 application I am able to see the library name, the class name but none of the methods or properties associated with them?

If anyone could please help me fix this problem, I have been stuck on it for quite a while!

Here is my class:

using System;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;

namespace VNDBUtils
{
public enum VNConstants : long
{
    cenMySQLDataStore = 32
}

[InterfaceType(ComInterfaceType.InterfaceIsDual)]
[Guid("CF4EFB82-6EE1-4A84-9CA9-07B135888B68")]
[ComVisible(true)]
public interface IVNSqlFormatter
{
    //Properties
    long DS_Type { get; set; }
    string DS_Query { get; set; }

    //Methods
    string Format_Entity(string strString);
    string MqStrMan_MakeStringEndWith(string strString, string strMatch);
    bool MqStrMan_StringEndsWith(string strString, string strMatch);
    string MqStrMan_MakeStringStartWith(string strString, string StrMatch);
    bool MqStrMan_StringStartsWith(string strString, string strMatch);
    string Right(string value, int length);
    string Left(string value, int maxLength);
    string Format_Value(string strString);
}



[ClassInterface(ClassInterfaceType.None)]
[Guid("3884D59D-AB76-41E7-82B6-21C66DBDCBF3")]
[ComVisible(true)]
public class VNSqlFormatter : IVNSqlFormatter
{

    private const string SQUARE_LEFT = "[";
    private const string SQUARE_RIGHT = "]";

    public long DS_Type { get; set; }
    public string DS_Query { get; set; }

    public string Format_Entity(string strString)
    {           
        strString = strString.Trim();

        if (DS_Type == (long)VNConstants.cenMySQLDataStore)
        {
            return strString;
        }
        else
        {
            return MqStrMan_MakeStringEndWith(MqStrMan_MakeStringStartWith(strString, SQUARE_LEFT), SQUARE_RIGHT);
        }

    }

    public string MqStrMan_MakeStringEndWith(string strString, string strMatch)
    {
        if (MqStrMan_StringEndsWith(strString, strMatch) == false)
        {
            return strString + strMatch;
        }
        else
        {
            return strString; 
        }

    }

    public bool MqStrMan_StringEndsWith(string strString, string strMatch)
    {
        return String.Equals(Right(strString, strMatch.Length), strMatch);

    }

    public string MqStrMan_MakeStringStartWith(string strString, string strMatch)
    {
        if (MqStrMan_StringStartsWith(strString, strMatch) == false)
        {
            return strMatch + strString;
        }
        else
        {
            return strString; 
        }
    }

    public bool MqStrMan_StringStartsWith(string strString, string strMatch)
    {
       return String.Equals(Left(strString, strMatch.Length), strMatch);
    }

    public string Right(string value, int length)
    {
        if (String.IsNullOrEmpty(value))
        {
            return String.Empty;
        }

        return value.Length <= length ? value : value.Substring(value.Length - length);
    }

    public string Left(string value, int maxLength)
    {
        if(String.IsNullOrEmpty(value))
        {
            return String.Empty; 
        }

        maxLength = Math.Abs(maxLength);
        return value.Length <= maxLength ? value : value.Substring(0, maxLength);
    }

    public string Format_Value(string strString)
    {
            return strString.Replace("'", "''");
    }

}

}

Answer 1

Have you edited the AssemblyInfo.cs file?

Typically, this is the default:

// Setting ComVisible to false makes the types in this assembly not visible 
// to COM components.  If you need to access a type in this assembly from 
// COM, set the ComVisible attribute to true on that type.
[assembly: ComVisible(false)]

// The following GUID is for the ID of the typelib if this project is exposed to COM
[assembly: Guid("e2e2a417-bd3d-414d-97f9-91196ce1c63a")]

You would need to set the [assembly: ComVisible(false)] to true .

Answer 2

Discussion in comments lead to the following, the ProgId attribute was not set.

[ClassInterface(ClassInterfaceType.None)]
[Guid("3884D59D-AB76-41E7-82B6-21C66DBDCBF3")]
[ComVisible(true)]
[ProgId("VNDBUtils.VNSqlFormatter")]
public class VNSqlFormatter : IVNSqlFormatter
{
    /* implementation information */
}

Answer 3

Thought this was too long to add as a comment to the other answer .

The ProgID should be generated automatically. And it seems like it should have already been generated as the same string you added manually.

According to Microsoft documentation Assembly to Type Library Conversion Summary - Exported Type Conversion:

The export process also automatically generates a programmatic identifier (ProgId) by combining the namespace and type name. For example, the ProgId generated for the managed LinkedList class shown in the previous examples is ABLinkedList.

Combining the namespace and type name can result in an invalid ProgId. A ProgId is limited to 39 characters and can contain no punctuation characters other than periods. To avoid these limitations, you can specify a ProgId in your source code by applying the ProgIdAttribute, rather than allowing the export process to generate an identifier for you.

If you take out the ProgID attribute just as a test, you could then inspect the typelib which is created upon compilation (with a tool like OleView) and see what ProgID it is generating. Maybe there is a possibility it generates a ProgID which is invalid to VB6, though it doesn't seem like that would be the case from the code in your example.