How to create a 1-Dimensional Array in C# with index starting at 1

Question

For multidimensional arrays Array.CreateInstance can be used to create non-zero index based arrays, but if you try that for a 1-dimensional arrays (vectors) as in e.g.:

Answer 1

Non-Zero based arrays DO exist in C, and there IS a way to create a 1's (or whatever) based array.

I fully agree that they are messy, and they should not be used for anything other than legacy stuff, but they are ESSENTIAL to interact with old COM libraries.

The most common place to run into this is working with the Microsoft.Office.Interop.Excel.Range object in the Excel library which still uses the old DCOM interface underneath.

Example:

/// 

    /// Makes the equivalent of a local Excel range that can be populated 
    ///  without leaving .net
    /// 
    /// number of rows in the table
    /// number of columns in the table
    /// a 1's based, 2 dimensional object array which can put back to Excel in one DCOM call.
    public static object[,] NewObjectArray(int iRows, int iCols)
    {

        int[] aiLowerBounds = new int[] { 1, 1 };
        int[] aiLengths = new int[] { iRows, iCols};

        return (object[,])Array.CreateInstance(typeof(object), aiLengths, aiLowerBounds);

    }

In this case, the reason this code is necessary is each DCOM call to excel is a cross-process call, and if you were to access cells one-at-a-time, you'd incur huge overhead, (either retrieving or setting values). An Excel range is a 1's based 2 dimensional array, and if one creates the array, and populates it locally, it can be pushed to excel in one cross-process call, creating an enormous performance improvement.