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How to skip empty cells while reading data from Excel using OpenXML?

I am trying to read data from Excel and store it into a DataTable using OpenXML. I want data in my DataTable as it is in Excel sheet but when there is a empty cell in Excel, it was not looking as expected.
Because code row.Descendants<Cell>().ElementAt(i) skips empty cells while reading data and in DataTable Rows and Columns are stored incorrectly. I resolved this issue using below code but when my excel has more than 26 columns, it is not working as expected and again data are stored in DataTable incorrectly.
(i.e., While reading data from AA, AB, AC columns)
Can someone help me to rewrite this code to handle this issue when there is more than 26 columns.
private static int CellReferenceToIndex(Cell cell)
{
int index = 0;
string reference = cell.CellReference.ToString().ToUpper();
foreach (char ch in reference)
{
if (Char.IsLetter(ch))
{
int value = (int)ch - (int)'A';
index = (index == 0) ? value : ((index + 1) * 26) + value;
}
else
{
return index;
}
}
return index;
}

You can use example below (taken from here and improved by few validations):
public static int GetColumnIndex(this Cell cell)
{
string columnName = string.Empty;
if (cell != null)
{
string cellReference = cell.CellReference?.ToString();
if (!string.IsNullOrEmpty(cellReference))
// Using `Regex` to "pull out" only letters from cell reference
// (leave only "AB" column name from "AB123" cell reference)
columnName = Regex.Match(cellReference, #"[A-Z]{1,3}").Value;
}
// Column name validations (not null, not empty and contains only UPPERCASED letters)
// *uppercasing may be done manually with columnName.ToUpper()
if (string.IsNullOrEmpty(columnName))
throw new ArgumentException("Column name was not defined.", nameof(columnName));
else if (!Regex.IsMatch(columnName, #"^[A-Z]{1,3}$"))
throw new ArgumentException("Column name is not valid.", nameof(columnName));
int index = 0;
int pow = 1;
// A - 1 iteration, AA - 2 iterations, AAA - 3 iterations.
// On each iteration pow value multiplies by 26
// Letter number (in alphabet) + 1 multiplied by pow value
for (int i = columnName.Length - 1; i >= 0; i--)
{
index += (columnName[i] - 'A' + 1) * pow;
pow *= 26;
}
// Index couldn't be greater than 16384
if (index >= 16384)
throw new IndexOutOfRangeException("Index of provided column name (" + index + ") exceeds max range (16384).");
return index;
}
All exception throws you can replace with return -1 and some kind of Log("...") if you have logging. Otherwise you may not be sure what's problem happened and why was returned -1.
Usage is obvious:
var cells = row.Descendants<Cell>();
foreach (Cell cell in cells)
{
int columnIndex = cell.GetColumnIndex();
// Do what you want with that
}
EDIT.
I'm not sure what you're trying to achieve. And what you mean here:
Because code row.Descendants<Cell>().ElementAt(i) skips empty cells...
I didn't see that. Look at example below:
Random ElementAt in range between 0 and Descendants<Cell>().Count() works too and shows both empty and non-empty cells:

Figure out max number of consecutive seats

I had an interviewer ask me to write a program in c# to figure out the max number of 4 members families that can sit consecutively in a venue, taking into account that the 4 members must be consecutively seated in one single row, with the following context:
N represents the number of rows availabe.
The Columns are labeled from the letter "A" to "K", purposely ommiting the letter "i" (in other words, {A,B,C,D,E,F,G,H,J,K})
M represents a list of reserved seats
Quick example:
N = 2
M = {"1A","2F","1C"}
Solution = 3
In the representation you can see that, with the reservations and the size given, only three families of 4 can be seated in a consecutive order.
How would you solve this? is it possible to not use for loops? (Linq solutions)
I got mixed up in the for loops when trying to deal with the reservations aray: My idea was to obtain all the reservations that a row has, but then I don't really know how to deal with the letters (Converting directly from letter to number is a no go because the missing "I") and you kinda need the letters to position the reserved sits anyway.
Any approach or insight on how to go about this problem would be nice.
Thanks in advance!

Here is another implementation.
I also tried to explain why certain things have been done.
Good luck.
private static int GetNumberOfAvailablePlacesForAFamilyOfFour(int numberOfRows, string[] reservedSeats)
{
// By just declaring the column names as a string of the characters
// we can query the column index by colulmnNames.IndexOf(char)
string columnNames = "ABCDEFGHJK";
// Here we transform the reserved seats to a matrix
// 1A 2F 1C becomes
// reservedSeatMatrix[0] = [0, 2] -> meaning row 1 and columns A and C, indexes 0 and 2
// reservedSeatMatrix[1] = [5] -> meaning row 2 and column F, index 5
List<List<int>> reservedSeatMatrix = new List<List<int>>();
for (int row = 0; row < numberOfRows; row++)
{
reservedSeatMatrix.Add(new List<int>());
}
foreach (string reservedSeat in reservedSeats)
{
int seatRow = Convert.ToInt32(reservedSeat.Substring(0, reservedSeat.Length - 1));
int seatColumn = columnNames.IndexOf(reservedSeat[reservedSeat.Length - 1]);
reservedSeatMatrix[seatRow - 1].Add(seatColumn);
}
// Then comes the evaluation.
// Which is simple enough to read.
int numberOfAvailablePlacesForAFamilyOfFour = 0;
for (int row = 0; row < numberOfRows; row++)
{
// Reset the number of consecutive seats at the beginning of a new row
int numberOfConsecutiveEmptySeats = 0;
for (int column = 0; column < columnNames.Length; column++)
{
if (reservedSeatMatrix[row].Contains(column))
{
// reset when a reserved seat is reached
numberOfConsecutiveEmptySeats = 0;
continue;
}
numberOfConsecutiveEmptySeats++;
if(numberOfConsecutiveEmptySeats == 4)
{
numberOfAvailablePlacesForAFamilyOfFour++;
numberOfConsecutiveEmptySeats = 0;
}
}
}
return numberOfAvailablePlacesForAFamilyOfFour;
}
static void Main(string[] args)
{
int familyPlans = GetNumberOfAvailablePlacesForAFamilyOfFour(2, new string[] { "1A", "2F", "1C" });
}

Good luck on your interview
As always, you will be asked how could you improve that? So you'd consider complexity stuff like O(N), O(wtf).
Underlying implementation would always need for or foreach. Just importantly, never do unnecessary in a loop. For example, if there's only 3 seats left in a row, you don't need to keep hunting on that row because it is not possible to find any.
This might help a bit:
var n = 2;
var m = new string[] { "1A", "2F", "1C" };
// We use 2 dimension bool array here. If it is memory constraint, we can use BitArray.
var seats = new bool[n, 10];
// If you just need the count, you don't need a list. This is for returning more information.
var results = new List<object>();
// Set reservations.
foreach (var r in m)
{
var row = r[0] - '1';
// If it's after 'H', then calculate index based on 'J'.
// 8 is index of J.
var col = r[1] > 'H' ? (8 + r[1] - 'J') : r[1] - 'A';
seats[row, col] = true;
}
// Now you should all reserved seats marked as true.
// This is O(N*M) where N is number of rows, M is number of columns.
for (int row = 0; row < n; row++)
{
int start = -1;
int length = 0;
for (int col = 0; col < 10; col++)
{
if (start < 0)
{
if (!seats[row, col])
{
// If there's no consecutive seats has started, and current seat is available, let's start!
start = col;
length = 1;
}
}
else
{
// If have started, check if we could have 4 seats.
if (!seats[row, col])
{
length++;
if (length == 4)
{
results.Add(new { row, start });
start = -1;
length = 0;
}
}
else
{
// // We won't be able to reach 4 seats, so reset
start = -1;
length = 0;
}
}
if (start < 0 && col > 6)
{
// We are on column H now (only have 3 seats left), and we do not have a consecutive sequence started yet,
// we won't be able to make it, so break and continue next row.
break;
}
}
}
var solution = results.Count;
LINQ, for and foreach are similar things. It is possible you could wrap the above into a custom iterator like:
class ConsecutiveEnumerator : IEnumerable
{
public IEnumerator GetEnumerator()
{
}
}
Then you could start using LINQ.

If you represent your matrix in simple for developers format, it will be easier. You can accomplish it either by dictionary or perform not so complex mapping by hand. In any case this will calculate count of free consecutive seats:
public static void Main(string[] args)
{
var count = 0;//total count
var N = 2; //rows
var M = 10; //columns
var familySize = 4;
var matrix = new []{Tuple.Create(0,0),Tuple.Create(1,5), Tuple.Create(0,2)}.OrderBy(x=> x.Item1).ThenBy(x=> x.Item2).GroupBy(x=> x.Item1, x=> x.Item2);
foreach(var row in matrix)
{
var prevColumn = -1;
var currColumn = 0;
var free = 0;
var div = 0;
//Instead of enumerating entire matrix, we just calculate intervals in between reserved seats.
//Then we divide them by family size to know how many families can be contained within
foreach(var column in row)
{
currColumn = column;
free = (currColumn - prevColumn - 1)/familySize;
count += free;
prevColumn = currColumn;
}
currColumn = M;
free = (currColumn - prevColumn - 1)/familySize;
count += free;
}
Console.WriteLine("Result: {0}", count);
}

find the row number of a datatable column containing specific value C#

I have a datatable in C# with a column called Point that contains various integer values. How do I find the row number of the first row that is equal to a specific value. E.g. Maybe I want to find the first time that the number 52 appears in the Point Column and it appears first at row 10. How do I find the value 10?
Note that I want to find the row number and not the value of another column at this position, hence why this question is different to:
Find row in datatable with specific id

A for loop is probably the simplest way. This answer returns the index of the row (row number) in the DataTable which matches a specific value.
int firstRow = 0;
for (int i = 0; i < dt.Rows.Count; i++)
{
var row = dt.Rows[i];
int point = Convert.ToInt32(row["Point"].ToString());
if (point == 52)
{
// i is the first row matching your condition
firstRow = i;
break;
}
}

The following may work for you:
DataTable table = new DataTable("SomeData");
table.Columns.Add("Point", typeof(int));
table.Rows.Add(5);
table.Rows.Add(7);
table.Rows.Add(52);
table.Rows.Add(2);
table.Rows.Add(1);
table.Rows.Add(4);
table.Rows.Add(9);
var row = table.AsEnumerable().Select((r, i) => new { Row = r, Index = i }).Where(x => (int)x.Row["Point"] == 52).FirstOrDefault();
int rowNumber = 0;
if (row != null)
rowNumber = row.Index + 1;
Note that in this example I give the row number, not the index that starts from zero.

Index was out of range. Must be non-negative and less than the size of the collection. 4

My datagridview has 4 rows. row[2] has the name of date1 and row[3] has the name of date2. I also tested this code with Cells[2] and Cell[3] instead of Cells name. But again i received the same error. The problem is that Index is not out of range. and is less than the size of the collection. This is my code:
for (int i = 0; i < dgv1frmModateEghamat.Rows.Count; i++)
{
DateTime date1 = Convert.ToDateTime(dgv1frmModateEghamat.SelectedRows[i].Cells["date1"].Value);
DateTime date2 = Convert.ToDateTime(dgv1frmModateEghamat.SelectedRows[i].Cells["date2"].Value);
TimeSpan span = date2.Subtract(date1);
int result = int.Parse(span.TotalDays.ToString());
if (result >= int.Parse(textBoxX2.Text))
{
dgv1frmModateEghamat.SelectedRows[i].Visible = true;
}
else
{
CurrencyManager cr = (CurrencyManager)BindingContext[dgv1frmModateEghamat.DataSource];
cr.SuspendBinding();
dgv1frmModateEghamat.SelectedRows[i].Visible = false;
}
}
But I see this error: Index was out of range. Must be non-negative and less than the size of the collection.

You are looping through Rows but indexing into SelectedRows. You need to loop through SelectedRows.
for (int i = 0; i < dgv1frmModateEghamat.SelectedRows.Count; i++)

dgv1frmModateEghamat.SelectedRows may have fewer items than dgv1frmModateEghamat.Rows.

C# Array, String, error

int i;
int [,] Prices = new int [2, 7]{{1,2,3,4,5,6,7},{700,600,500,400,300,200,100}};
string[,] City = new string [2,1]{{"A"},{"B"}};
bool found = false;
for (i = 0; i <= City.Length -1; i++)
// for (y = 0; y <= City.Length - 1; y++)
{
if (LstDestinationCity.Text == City[i]) <<-- i get error here
{
im planing to do a program that if i select A city i get first row if B city i get 2 row

I think that's because City[i] "don't contain anything" you should check City[i,0]
if (LstDestinationCity.Text == City[i,0])// this should access the first element which is the text you are looking for

I would rather do it as
if (LstDestinationCity.Text == City[i,i])
{
// ...
}

Your City variable does not need to be a two dimensional array. If you change it to a one dimensional array you can access the values with one index instead of 2.
string[] City = new string [2]{"A","B"};