How to retrieve efficiently all strings from a large excel documents

See more:

C#

.NET

MS-Excel

The Excel spreadsheet should be read by .NET. It is very efficient to read all values from the active range by using the property Value. This transfers all values in a two dimensional array, by one single call to Excel.

However reading strings is not possible for a range which contains more than one single cell. Therefor we have to iterate over all cells and use the Text property. This shows very poor performance for larger document.

The reason of using strings rather than values is to obtains the correct format (for instance for dates or the number of digits).

Here is a sample code written in C# to demonstrate the approach.

static void Main(string[] args)
{
    Excel.Application xlApp = 
        (Excel.Application)System.Runtime.InteropServices.Marshal.
            GetActiveObject("Excel.Application");

	var worksheet = xlApp.ActiveSheet;
	var cells = worksheet.UsedRange();

	// read all values in array -> fast
	object[,] arrayValues = cells.Value;

	// create array for text of the same extension
	object[,] arrayText = (object[,])Array.CreateInstance(typeof(object),
            new int[] {
                arrayValues.GetUpperBound(0),
                arrayValues.GetUpperBound(1)
            },
            new int[] {
                arrayValues.GetLowerBound(0),
                arrayValues.GetLowerBound(1)
           });

	// read text for each cell -> slow
	for (int row = arrayValues.GetUpperBound(0);
             row <= arrayValues.GetUpperBound(0);
             ++row)
        {
            for (int col = arrayValues.GetUpperBound(0);
                 col <= arrayValues.GetUpperBound(1);
                 ++col)
            {
                object obj = cells[row, col].Text;
                arrayText[row, col] = obj;
            }
	}
}

The question is, if there is a more efficient way to read the complete string content from an Excel document.

What I have tried:

One idea was to use cells.Copy to copy the content to the clipboard to get it from there. However this has some restrictions and could of course interfere with users which are working with the clipboard at the same time.