在C＃中测试空的DataRow

Question

what I'm trying to do: I have a large datatable, and I'm going through a list of strings where some of them are in the datatable and some aren't. I need to make a list of those that are, and count those that aren't. This is my code part:

DataRow[] foundRows;

foundRows = DTgesamt.Select("SAP_NR like '%"+SAP+"%'");
if (AreAllCellsEmpty(foundRows[0]) == false && !(foundRows[0]==null))
{
    list.Add(SAP);
}
else
{
   notfound++; 
}


public static bool AreAllCellsEmpty(DataRow row)
{
    if (row == null) throw new ArgumentNullException("row");

    for (int i = row.Table.Columns.Count - 1; i >= 0; i--)
    {
        if (!row.IsNull(i))
        {
            return false;
        }
    }

    return true;
}

DTgesamt ist a large DataTable. "SAP" is a string that is in the first column of the DataTable, but not all of them are included. I want to count the unfound ones with the int "notfound". The problem is, the Select returns an empty DataRow {System.Data.DataRow[0]} when it finds nothing. I'm getting the errormessage Index out of array area. The two statements in the if-clause are what I read on the internet but they don't work. With only the 2nd statement it just adds all numbers to the list, with the first it still gives this error. Thanks for any help :)

Answer 1

check count of items in foundRows array to avoid IndexOutOfRange exception

foundRows = DTgesamt.Select("SAP_NR like '%"+SAP+"%'");
if (foundRows.Length > 0 && AreAllCellsEmpty(foundRows[0])==false)    
    list.Add(SAP);    
else    
    notfound++;    

Answer 2

The found cells cannot be empty. Your select statement would be wrong. So what you actually need is:

if (DTgesamt.Select("SAP_NR like '%"+SAP+"%'").Any())
{
    list.Add(SAP);
}
else
{
   notfound++; 
}

You probably don't even need the counter, when you can calculate the missed records based on how many SAP numbers you had and how many results you got in list .

If you have an original list or array of SAP numbers, you could shorten your whole loop to:

var numbersInTable = originalNumbers.Where(sap => DTgesamt.Select("SAP_NR like '%"+sap+"%'").Any()).ToList();

var notFound = originalNumbers.Count - numbersInTable.Count;