Executing C DLL from C# - fatalexecutionengineerror + accessviolationexception + the error code is 0xc0000005.

//Define Code internal static class UnsafeMethods { [DllImport("kernel32.dll", SetLastError = true)] internal extern static IntPtr LoadLibrary(string libraryName); [DllImport("kernel32.dll", SetLastError = true)] internal extern static bool FreeLibrary(IntPtr hModule); [DllImport("kernel32.dll", SetLastError = true)] internal extern static IntPtr GetProcAddress(IntPtr hModule, string procName); }

public class Simulator : IDisposable { //Define Delegates. [UnmanagedFunctionPointer(CallingConvention.Cdecl)] delegate void PopulateInputsDelegate(int nbrInputArgs, double[] inp); [UnmanagedFunctionPointer(CallingConvention.Cdecl)] delegate void GetOutputsDelegate(double[] inputArgs); [UnmanagedFunctionPointer(CallingConvention.Cdecl)] delegate void LoadCalsDelegate(string outputFileName, string inputFileName, int writeOutputFile); [UnmanagedFunctionPointer(CallingConvention.Cdecl)] delegate void InitializeMethods_Sim(); [UnmanagedFunctionPointer(CallingConvention.Cdecl)] delegate void TimeBasedEvent();

    //Define Function Pointers.
    PopulateInputsDelegate PopulateInputs;
    GetOutputsDelegate GetOutputs;
    LoadCalsDelegate LoadCals;
    InitializeMethods_Sim funcInitializeMethods_Sim;


    TimeBasedEvent MngEPTR_EngineCycle;
    TimeBasedEvent MngEPTR_ExhTMP_12p5ms;
    TimeBasedEvent MngEPTR_ExhTMP_100ms;

    //Define Handles
    IntPtr dllHandle;
    IntPtr funcaddrPopulateInputs;
    IntPtr funcaddrGetOutputs;
    IntPtr funcaddrLoadCals;
    IntPtr funcaddrInitializeMethods_Sim;
    IntPtr funcaddrMngEPTR_ExhTMP_12p5ms;
    IntPtr funcaddrMngEPTR_ExhTMP_100ms;
    IntPtr funcaddrMngEPTR_EngineCycle;
public void InitializeSimulator() { try { //Load this.dllHandle = UnsafeMethods.LoadLibrary(this.model.OutputDLLPath); if (dllHandle == IntPtr.Zero) { int errorCode = Marshal.GetLastWin32Error(); throw new Exception(string.Format("Failed to load library (ErrorCode: {0})", errorCode)); };

            funcaddrPopulateInputs = UnsafeMethods.GetProcAddress(dllHandle, "PopulateInputs");
            PopulateInputs = Marshal.GetDelegateForFunctionPointer(funcaddrPopulateInputs, typeof(PopulateInputsDelegate)) as PopulateInputsDelegate;

            funcaddrGetOutputs = UnsafeMethods.GetProcAddress(dllHandle, "GetOutputs");
            GetOutputs = Marshal.GetDelegateForFunctionPointer(funcaddrGetOutputs, typeof(GetOutputsDelegate)) as GetOutputsDelegate;

            funcaddrLoadCals = UnsafeMethods.GetProcAddress(dllHandle, "LoadCals");
            LoadCals = Marshal.GetDelegateForFunctionPointer(funcaddrLoadCals, typeof(LoadCalsDelegate)) as LoadCalsDelegate;

            funcaddrInitializeMethods_Sim = UnsafeMethods.GetProcAddress(dllHandle, "InitializeMethods_Sim");
            funcInitializeMethods_Sim = Marshal.GetDelegateForFunctionPointer(funcaddrInitializeMethods_Sim, typeof(InitializeMethods_Sim)) as InitializeMethods_Sim;

            funcaddrMngEPTR_ExhTMP_12p5ms = UnsafeMethods.GetProcAddress(dllHandle, "_12p5Methods_Sim");
            MngEPTR_ExhTMP_12p5ms = Marshal.GetDelegateForFunctionPointer(funcaddrMngEPTR_ExhTMP_12p5ms, typeof(TimeBasedEvent)) as TimeBasedEvent;

            funcaddrMngEPTR_ExhTMP_100ms = UnsafeMethods.GetProcAddress(dllHandle, "_100Methods_Sim");
            MngEPTR_ExhTMP_100ms = Marshal.GetDelegateForFunctionPointer(funcaddrMngEPTR_ExhTMP_100ms, typeof(TimeBasedEvent)) as TimeBasedEvent;

            funcaddrMngEPTR_EngineCycle = UnsafeMethods.GetProcAddress(dllHandle, "_EngineCycle_Sim");
            MngEPTR_EngineCycle = Marshal.GetDelegateForFunctionPointer(funcaddrMngEPTR_EngineCycle, typeof(TimeBasedEvent)) as TimeBasedEvent;

        }
private void SimulateEventBasedGroup(MeasurementData inputMeasuredData) { // Log the method entry. Logger.Instance.Debug(Constants.FUNCTION_ENTERED_LOG);

        try
        {
            this.inputMeasuredData = new MeasurementData();
            this.inputMeasuredData = inputMeasuredData;

            ////Load Cals
            //this.LoadCals.Invoke(this.GetCalsArray());

            int rowCount = this.inputMeasuredData.SignalGroup.RowCount;

            //Load Data & execute EngineCycle
            for (rowIndex = 0; rowIndex < rowCount; rowIndex++)
            {
                this.PopulateInputs.Invoke(this.xSignals.Count, this.GetInputMeasuredSignalArray());

                //Execute Engine Cycle
                this.MngEPTR_EngineCycle.Invoke(); //MngEPTR_EngineCycle - C code method giving exception - Help needed

                this.SetOutputMeasurementData();
                //this.SetEngineCycleOutput();
            }
        }
        catch 
        {

        }
} }

Exceptions caught - Managed Debugging Assistant 'FatalExecutionEngineError' has detected a problem in 'C:\Application.exe'. Additional Information: The runtime has encountered a fatal error. The address of the error was at 0x719a9a14, on thread 0x2f84. The error code is 0xc0000005. This error may be a bug in the CLR or in the unsafe or non-verifiable portions of user code. Common sources of this bug include user marshaling errors for COM-interop or PInvoke, which may corrupt the stack.

Sometimes I get : 1.) First chance execption at a 0x********. Access Violation Written Location 0x*****. 2.) R6013 - Attempt to initialize the CRT more than once.

Please help me in resolving the issue on urgent basis. Thanks in advance.