The exception message is 'Unable to load DLL 'Final1_dll.dll

Question

hi i am software engineer. For the last few days I am trying to pass the json format data to the wcf web service using using framework 4.0 and in the service i call the dll which will perform some action on the json data. the dll namely Final1_dll.dll when I check it on the local IIS it's working fine but when I upload this to the server so its give me error of "The exception message is 'Unable to load DLL 'Final1_dll.dll': The specified module could not be found. (Exception from HRESULT: 0x8007007E)".

[DllImport("Final1_dll.dll", CharSet = CharSet.Ansi, CallingConvention=CallingConvention.StdCall)]

        public static extern IntPtr PtrReturnAPI02(char[] abc);

public string DemosData(Stream data1) {

            // convert Stream Data to StreamReader

            StreamReader reader = new StreamReader(data1);

            // Read StreamReader data as string

            string xmlString = reader.ReadToEnd();

            if (IsJson(xmlString))

            {

                IntPtr pStr = PtrReturnAPI02(xmlString.ToCharArray());

                string str = Marshal.PtrToStringAnsi(pStr);

                Marshal.FreeHGlobal(pStr);

                pStr = IntPtr.Zero;

                return str;

            }

            else

            { return "Input was not in a correct format."; }

            // PtrReturnAPI02(xmlString.ToCharArray());

            }

        public static bool IsJson(string input)

        {

            input = input.Trim();

            return input.StartsWith("{") && input.EndsWith("}")

                   || input.StartsWith("[") && input.EndsWith("]");

        } 

[ServiceContract]

    interface IManagedCodeService

    {

[OperationContract(Name="DemoData")]

        [WebInvoke(Method = "POST", ResponseFormat = WebMessageFormat.Json, BodyStyle = WebMessageBodyStyle.Wrapped, UriTemplate = "DemoData")]

        string DemosData(Stream data1);
}

I need some suggestions ASAP. Thanks in advance.