Excel ExcelDNA C# / Try to copy Bloomberg BDH() behavior (writing Array after a web request)

Question

I want to copy Bloomberg BDH behavior.

BDH makes a web request and write an array (but doesn\'t return an array style). During this web request, the function returns \"#

Answer 1

My issue was :

• writing dynamic array

• data are retrieved asynchronous via a webservice

After discussing with Govert, I chose to take a result as an array and not to copy Bloomberg functions (write an array but return a single value).

Finally, to solve my issue, I used http://excel-dna.net/2011/01/30/resizing-excel-udf-result-arrays/ and reshape the resize() function.

This code is not RTD.

The code belows works in a .dna file

 ResizeJobs = new Queue();
        static Dictionary JobIsDone = new Dictionary();

        // This function will run in the UDF context.
        // Needs extra protection to allow multithreaded use.
        public static object Resize(object args)
        {
            ExcelReference caller = XlCall.Excel(XlCall.xlfCaller) as ExcelReference;
            if (caller == null)
                return ExcelError.ExcelErrorNA;

            if (!JobIsDone.ContainsKey(GetHashcode(caller)))
            {
                BackgroundWorker(caller);
                return ExcelError.ExcelErrorNA;
            }
            else
            {
                // Size is already OK - just return result
                object[,] array = (object[,])JobIsDone[GetHashcode(caller)];
                JobIsDone.Remove(GetHashcode(caller));
                return array;
            }
        }

        /// 

        /// Simulate WebServiceRequest
        /// 
        /// 
        /// 
        /// 
        static void BackgroundWorker(ExcelReference caller)
        { 
            BackgroundWorker bw = new BackgroundWorker();
            bw.DoWork += (sender, args) =>
            {
                Thread.Sleep(3000);
            };
            bw.RunWorkerCompleted += (sender, args) =>
            {
                // La requete
                Random r = new Random();
                object[,] array = ResizeTest.MakeArray(r.Next(10), r.Next(10));

                JobIsDone[GetHashcode(caller)] = array;
                int rows = array.GetLength(0);
                int columns = array.GetLength(1);
                EnqueueResize(caller, rows, columns);
                AsyncRunMacro("DoResizing");
            };

            bw.RunWorkerAsync();
        }

        static string GetHashcode(ExcelReference caller)
        {
            return caller.SheetId + ":L" + caller.RowFirst + "C" + caller.ColumnFirst;
        }


        static void EnqueueResize(ExcelReference caller, int rows, int columns)
        {
            ExcelReference target = new ExcelReference(caller.RowFirst, caller.RowFirst + rows - 1, caller.ColumnFirst, caller.ColumnFirst + columns - 1, caller.SheetId);
            ResizeJobs.Enqueue(target);
        }

        public static void DoResizing()
        {
            while (ResizeJobs.Count > 0)
            {
                DoResize(ResizeJobs.Dequeue());
            }
        }

        static void DoResize(ExcelReference target)
        {
            try
            {
                // Get the current state for reset later

                XlCall.Excel(XlCall.xlcEcho, false);

                // Get the formula in the first cell of the target
                string formula = (string)XlCall.Excel(XlCall.xlfGetCell, 41, target);
                ExcelReference firstCell = new ExcelReference(target.RowFirst, target.RowFirst, target.ColumnFirst, target.ColumnFirst, target.SheetId);

                bool isFormulaArray = (bool)XlCall.Excel(XlCall.xlfGetCell, 49, target);
                if (isFormulaArray)
                {
                    object oldSelectionOnActiveSheet = XlCall.Excel(XlCall.xlfSelection);
                    object oldActiveCell = XlCall.Excel(XlCall.xlfActiveCell);

                    // Remember old selection and select the first cell of the target
                    string firstCellSheet = (string)XlCall.Excel(XlCall.xlSheetNm, firstCell);
                    XlCall.Excel(XlCall.xlcWorkbookSelect, new object[] {firstCellSheet});
                    object oldSelectionOnArraySheet = XlCall.Excel(XlCall.xlfSelection);
                    XlCall.Excel(XlCall.xlcFormulaGoto, firstCell);

                    // Extend the selection to the whole array and clear
                    XlCall.Excel(XlCall.xlcSelectSpecial, 6);
                    ExcelReference oldArray = (ExcelReference)XlCall.Excel(XlCall.xlfSelection);

                    oldArray.SetValue(ExcelEmpty.Value);
                    XlCall.Excel(XlCall.xlcSelect, oldSelectionOnArraySheet);
                    XlCall.Excel(XlCall.xlcFormulaGoto, oldSelectionOnActiveSheet);
                }
                // Get the formula and convert to R1C1 mode
                bool isR1C1Mode = (bool)XlCall.Excel(XlCall.xlfGetWorkspace, 4);
                string formulaR1C1 = formula;
                if (!isR1C1Mode)
                {
                    // Set the formula into the whole target
                    formulaR1C1 = (string)XlCall.Excel(XlCall.xlfFormulaConvert, formula, true, false, ExcelMissing.Value, firstCell);
                }
                // Must be R1C1-style references
                object ignoredResult;
                XlCall.XlReturn retval = XlCall.TryExcel(XlCall.xlcFormulaArray, out ignoredResult, formulaR1C1, target);
                if (retval != XlCall.XlReturn.XlReturnSuccess)
                {
                    // TODO: Consider what to do now!?
                    // Might have failed due to array in the way.
                    firstCell.SetValue("'" + formula);
                }
            }
            finally
            {
                XlCall.Excel(XlCall.xlcEcho, true);
            }
        }

        // Most of this from the newsgroup: http://groups.google.com/group/exceldna/browse_thread/thread/a72c9b9f49523fc9/4577cd6840c7f195
        private static readonly TimeSpan BackoffTime = TimeSpan.FromSeconds(1); 
        static void AsyncRunMacro(string macroName)
        {
            // Do this on a new thread....
            Thread newThread = new Thread( delegate ()
            {
                while(true) 
                { 
                    try 
                    {
                        RunMacro(macroName);
                        break; 
                    } 
                    catch(COMException cex) 
                    { 
                        if(IsRetry(cex)) 
                        { 
                            Thread.Sleep(BackoffTime); 
                            continue; 
                        } 
                        // TODO: Handle unexpected error
                        return; 
                    }
                    catch(Exception ex) 
                    { 
                        // TODO: Handle unexpected error
                        return;
                    } 
                }
            });
            newThread.Start();
        }

        static void RunMacro(string macroName)
        {
            object xlApp = null;       
            try
            {
                xlApp = ExcelDnaUtil.Application;
                xlApp.GetType().InvokeMember("Run", BindingFlags.InvokeMethod, null, xlApp, new object[] {macroName});
            }
            catch (TargetInvocationException tie)
            {
                throw tie.InnerException;
            }
            finally
            {
                Marshal.ReleaseComObject(xlApp);
            }
        }

        const uint RPC_E_SERVERCALL_RETRYLATER = 0x8001010A; 
        const uint VBA_E_IGNORE = 0x800AC472; 
        static bool IsRetry(COMException e) 
        { 
            uint errorCode = (uint)e.ErrorCode; 
            switch(errorCode) 
            { 
                case RPC_E_SERVERCALL_RETRYLATER: 
                case VBA_E_IGNORE: 
                    return true; 
                default: 
                    return false; 
            }
        }
    } 
]]>