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c# – Cannot perform runtime binding on a null reference exception

Posted by: admin March 9, 2020 Leave a comment

Questions:

I’m trying to find the dimensions of an Excel table using C# by finding the first null cell within the first column (which consists of dates) and the header row.

Here’s the code I’m using right now:

public static void findingTableBounds()
    {
        string dateCol = "";
        ArrayList dateColumn = new ArrayList();
        ArrayList numberOfColumns = new ArrayList();

        for (int column = 1; column < currentRow; column++)
        {
            dateCol = ((Excel.Range)workSheet.Cells[currentRow, 1]).Value2.ToString();
            if (dateCol != "")
            {
                dateColumn.Add(dateCol);
                currentRow++;
                totalRow++;
                Console.WriteLine("Total Row: {0}", totalRow);            
            }
            else
            {
                Console.WriteLine("Total Row: {0}", totalRow);
                currentRow = 2;
            }
        }

**Note: There is a closing bracket for this method, I didn’t include it because there’s another for loop that does the exact same thing as the above code but only for how many columns there are.

The error occurs at “dateCol = ((Excel.Range)workSheet.Cells[currentRow, 1]).Value2.ToString();” I’m pretty sure it happens because I’m trying to assign a null value (the cell) to dateCol (a string) when string is a non-nullable type. Unfortunately I’m not sure how to solve the problem.

How to&Answers:

Applying a null value to a string is doable, but if
((Excel.Range)workSheet.Cells[currentRow, 1]).Value2 is null, then it doesn’t have a function ToString() is not a function, so trying to execute it doesn’t work. Does it say what type of exception it is? because there might be a bigger problem…

Answer:

In regards to the above post (I don’t have enough reputation to comment on it)

For the sake of helping other lost souls, I upped this post and will just add:

if (((Excel.Range)workSheet.Cells[currentRow, 1]).Value2 != null) {…}.
– Sylvain Feb 16 ’15 at 21:07

I had an issue and used this, but found that, in my case at least, I changed this to:

if (excelWorksheet.Cells[row, column].Value2 != null)
{
  return ((Excel.Range)excelWorksheet.Cells[row, column]).Value2.ToString();
}
return "No data";

which worked for my particular case, at least. Having the Excel.Range portion in the if created errors.