Using the Essbase C API with C# - Initialisation

Essbase C API and .Net does not appear to be the hottest topic on the net, probably for obvious reasons, but somebody might find this useful. Working with the Essbase C API is fairly intuitive (after a while) and if imagination helps great products can come out.

Here are the steps to get the Essbase C API working in C# :

1.Install the Essbase Client and set the ESSBASE_PATH environment variable to “X:\Oracle\Middleware\EPMSystem11R1\products\Essbase\EssbaseClient”

2.Alternatively copy the Essbase API to a folder and set the ESSBASE_PATH to point to that folder. This makes for an easier deployment.

3.Create a new project in VS and add the following classes:

public class EssbaseTypes

{

[DllImport("essapinu.dll", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]

static internal extern uint EssInit(ref ESS_INIT_T EssInitStruct, ref uint EssHInst);

[DllImport("essapinu.dll", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]

static internal extern uint EssTerm(uint EssHInst);

}

public delegate uint FcnPtr();

[StructLayout(LayoutKind.Sequential, Pack = 1)]

public struct ESS_INIT_T

{

   public uint Version;

   public uint UserContext;

   public ushort MaxHandles;

   public uint MaxBuffer;
   public string LocalPath;

   public string MessageFile;

   public FcnPtr AllocFunc;

   public FcnPtr ReallocFunc;

   public FcnPtr FreeFunc;

   public FcnPtr MessageFunc;

   public string HelpFile;

   public uint Ess_System;

   public uint usApiType;

}

4.Using the code:

string essApiPath = @"C:\Oracle\Middleware\EPMSystem11R1\products\Essbase\EssbaseClient\bin\";

           

// Create initialisation structure

ESS_INIT_T essInit = new ESS_INIT_T();

essInit.Version = 0x000B1200;

essInit.UserContext = 0;

essInit.MaxHandles = 0;

essInit.MaxBuffer = 0;

essInit.LocalPath = essApiPath;

essInit.MessageFile = essApiPath + "essbase.mdb";

essInit.AllocFunc = null;

essInit.ReallocFunc = null;

essInit.FreeFunc = null;

essInit.MessageFunc = null;

essInit.HelpFile = essApiPath + "essapiw.hlp";

essInit.Ess_System = 0;

essInit.usApiType = 0x0002;

// instance handle

uint essHInst = 0;

// The errNum is 0 when successful

uint errNum1 = EssbaseTypes.EssInit(ref essInit, ref essHInst);

if (errNum1 == 0)

{

// Code goes here

uint errNum2 = EssbaseTypes.EssTerm(essHInst);

}

5. The errNum should be 0 in case of a successful initialisation. Any other code indicates an error. Errors are usually related to the essbase api path and the ESSBASE_PATH variable.

The value for Version in ESS_INIT_T can be found in file essapi.h. For 11.1.2 the version is 0x000B1200.