How to use aws-encryption-sdk.dll (C language) in C#?

See more:

C

DLL

C#7.0

I need to call a function which is in aws-encryption-sdk dll in my console application.But i am getting error when the function is called. Can someone guide me how to proceed for this.

What I have tried:

using System.Runtime.InteropServices;
public class Program
{
   [DllImport(@"C:\Users\Abc\Documents\visual studio 2015\Projects\ConsoleApplication4\ConsoleApplication4\aws-encryption-sdk.dll", EntryPoint = "aws_cryptosdk_keyring_on_decrypt", CallingConvention = CallingConvention.StdCall)]
        public static extern void aws_cryptosdk_keyring_on_decrypt(ref IntPtr value);
        static void Main(string[] args)
        {
            int value = 6;
            IntPtr sptr = Marshal.StringToHGlobalAnsi((value).ToString());
            aws_cryptosdk_keyring_on_decrypt(ref sptr);
            Console.WriteLine("called");
            Console.Read();
        }
    }