Creating c# library for mt4

[Cagatay Tezsezen]

I have worked on a simple DLL for mt4 by using visual studio 2013 c#. I added RGiesecke modules by using NuGet packeges. I can call simple procedures when it has only integer values. But when the function in the library has string values, mt4 cant find the function. Also, it makes wrong results for double or floating math operations. Does anyone have any experience on c# - mt4 connections.

[Cagatay Tezsezen]

I tried with C++, exactly the same code in https://www.mql5.com/en/articles/18. Below is the message I get. 

2016.05.19 21:08:38.642    2012.01.02 02:00  Cannot load 'CDLLsample.dll' [126]

I tried changing MFU as described in comments, and also compiled with x64, still the same error code 126. 

[Marco vd Heijden]

Cagatay Tezsezen:

I tried with C++, exactly the same code in https://www.mql5.com/en/articles/18. Below is the message I get. 

2016.05.19 21:08:38.642    2012.01.02 02:00  Cannot load 'CDLLsample.dll' [126]

I tried changing MFU as described in comments, and also compiled with x64, still the same error code 126. 

https://www.mql5.com/en/forum/103454

[Cagatay Tezsezen]

Marco vd Heijden:
https://www.mql5.com/en/forum/103454

Thank you for the answer. I found that registering the directories of libraries are not enough. One must copy all necessary lib and dll files to expert directory. Aso, it is not enough to copy them to include directory. But still there are strange problems that has to be solved. I can return integer, double or any number. However, I can not return back a string.

[Anton Nel]

Cagatay Tezsezen:
I have worked on a simple DLL for mt4 by using visual studio 2013 c#. I added RGiesecke modules by using NuGet packeges. I can call simple procedures when it has only integer values. But when the function in the library has string values, mt4 cant find the function. Also, it makes wrong results for double or floating math operations. Does anyone have any experience on c# - mt4 connections.

Try compile with x86 not x64.

[Anton Nel]

Cagatay Tezsezen:
Thank you for the answer. I found that registering the directories of libraries are not enough. One must copy all necessary lib and dll files to expert directory. Aso, it is not enough to copy them to include directory. But still there are strange problems that has to be solved. I can return integer, double or any number. However, I can not return back a string.

Answer is mql4_ansi2unicode. You can google this for more information.

[Cagatay Tezsezen]

Anton Nel:
Answer is mql4_ansi2unicode. You can google this for more information.

Hi Anton.

Happy to see you.  I compile with 86.

I noticed Foating values are also passed wrong to mt4. Only integers are being sent correctly. What d you think the reason is?

[Anton Nel]

Cagatay Tezsezen:

Hi Anton.

Happy to see you.  I compile with 86.

I noticed Foating values are also passed wrong to mt4. Only integers are being sent correctly. What d you think the reason is?

What about "double" instead of "float"?

[Cagatay Tezsezen]

Anton Nel:
What about "double" instead of "float"?

Same. It sends a value but the value is not as expected.

[Anton Nel]

Cagatay Tezsezen:
Same. It sends a value but the value is not as expected.

What does the value look like? Example?

[Cagatay Tezsezen]

Anton Nel:
What does the value look like? Example?

Thank you very much Anton. I solved the problem about strings. I did not work on double and float problem yet, because I have another issue. I try to export a DLL function to mt4. The red line gives an error message when trying to load to mt4: Unhandled exception 0xE0434352.

  [DllExport("readmysql", CallingConvention = CallingConvention.StdCall)]
        public static string readmysql(string databasename, string tablename, string refereanceword, string columnname, string lookupcolumn)
        {
   
        string myConnectionString = "server=localhost;uid=root;" + "pwd=000000;database=trytabase;";

            MySqlCommand mcd;
            MySqlDataReader mdr;
            string getvalue;


            MySql.Data.MySqlClient.MySqlConnection conn;
            conn = new MySql.Data.MySqlClient.MySqlConnection();

            conn.ConnectionString = myConnectionString;

I appreciate any comment on that matter