C#

<br />
static void TestLINQGroupBy()<br />
        {<br />
            #region Construct dummy data<br />
            Random rnd;<br />
            IList<string> Measures = new List<string>() { "eps", "bps", "close" };<br />
            IList<string> Symbols = new List<string>() { "0001HK", "0002HK", "0003HK" };<br />
            DataTable TestPrice = new DataTable("TestPrice");<br />
            DataColumn c = null;<br />
            DataRow newRw = null;<br />
<br />
            DataColumn[] PKs = new DataColumn[3];<br />
            c = new DataColumn("Symbol", typeof(string));<br />
            TestPrice.Columns.Add(c);<br />
            PKs[0] = c;<br />
<br />
            c = new DataColumn("Measure", typeof(string));<br />
            TestPrice.Columns.Add(c);<br />
            PKs[1] = c;<br />
<br />
            c = new DataColumn("RecordDate", typeof(DateTime));<br />
            TestPrice.Columns.Add(c);<br />
            PKs[2] = c;<br />
            <br />
            TestPrice.Columns.Add("Value", typeof(double));<br />
            TestPrice.PrimaryKey = PKs;<br />
            <br />
            foreach (string Symbol in Symbols)<br />
            {<br />
                foreach (string Measure in Measures)<br />
                {<br />
                    for (int iter = 1; iter < 12; iter++)<br />
                    {<br />
                        newRw = TestPrice.NewRow();<br />
                        newRw["Symbol"] = Symbol;<br />
                        newRw["Measure"] = Measure;<br />
                        rnd = new Random((Symbol + Measure + iter).GetHashCode());<br />
                        newRw["Value"] = rnd.NextDouble();<br />
                        newRw["RecordDate"] = new DateTime(DateTime.Now.Year, iter, 1);<br />
                        TestPrice.Rows.Add(newRw);<br />
                    }<br />
                }<br />
            }<br />
            #endregion<br />
<br />
            var q = from rw in TestPrice.Select()<br />
                    group rw by new {Key1=rw["Symbol"], Key2=rw["Measure"]} into key<br />
                    select key;<br />
            foreach (var k in q)<br />
            {<br />
                Console.WriteLine(k);<br />
            }<br />
            return;<br />
        }<br />

typedef enum _MAPI_APN_TYPE
{
	MAPI_APN_PRIMARY = 0,
	MAPI_APN_ACTIVATION,

}MAPI_APN_TYPE;

typedef struct _MAPI_APN_DATA
{
	wchar_t wcApn[80];
	wchar_t wcUsername[80];
	wchar_t wcPassword[80];
	wchar_t wcDialNumber[80];

}MAPI_APN_DATA, * LPMAPI_APN_DATA;

typedef struct _MAPI_CORE_PATH
{
	wchar_t	strPath     [ 260 ];

}MAPI_CORE_PATH, *LPMAPI_CORE_PATH;


***** c++ function that works: *******
MAPI_APN_DATA data;
MAPI_CORE_PATH path;
memset( &path, 0, sizeof( MAPI_CORE_PATH ) );
result = M_API_GetApnData( &path, MAPI_APN_ACTIVATION, &data );

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
public struct MAPI_APN_DATA
{
	[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 80)]
	public string apn;

	[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 80)]
	public string username;

	[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 80)]
	public string password;

	[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 80)]
	public string dialNumber;
}
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
public struct MAPI_CORE_PATH
{
	[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 260)]
	public string strPath;
}
public enum MAPI_APN_TYPE
{
	MAPI_APN_PRIMARY = 0,
	MAPI_APN_ACTIVATION,
};

[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
private delegate MAPI_RESULT M_API_GetApnData(ref MAPI_CORE_PATH path, MAPI_APN_TYPE apn_type, ref MAPI_APN_DATA data);
private M_API_GetApnData             fnMGetApnData;

//Init function delegates
pFunction = MbmFramework.Native.GetProcAddress(pMClientDll, "M_API_GetApnData");
fnMGetApnData = (M_API_GetApnData)Marshal.GetDelegateForFunctionPointer(pFunction, typeof(M_API_GetApnData));

//And the method that calls fnMGetApnData and gives System.AccessViolationExceptionMessage
MAPI_APN_DATA data = new MAPI_APN_DATA();
MAPI_CORE_PATH path = new MAPI_CORE_PATH();
MAPI_RESULT apiRes = fnMGetApnData(ref path, MAPI_APN_TYPE.MAPI_APN_ACTIVATION, ref data);

Dictionary <string,int> dic = new ...
 
string [] arr = {"hello","world"};
 
foreach (var str in arr)
{
dic.Add({0},str, str.Length);
}