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c# – EPPlus – Working with multiple columns by index rather than Alphabetical Representation

Posted by: admin March 9, 2020 Leave a comment

Questions:

I am using EPPlus in my .Net project to output some data into an Excel worksheet.

Suppose I wanted to format Columns E-G with a specific format. Using EPPlus, I know I can do it as follows:

wks.Cells("E:G").Style.Numberformat.Format = ...

Now, I’m wondering, suppose I wanted to do the same, but by referencing the columns by their index numbers rather than their alphabetical representation – In theory something looking like this:

wks.Columns("5:7").Style.Numberformat.Format = ...

Now, I know that it would work if I did something like this:

wks.Cells(1,5,wks.Dimension.End.Row,7).Style.Numberformat.Format = ...

But I’m hoping there’s a better / nicer way to do this in EPPlus. Any thoughts / suggestions?

Thanks!!

How to&Answers:

As an answer to my own question for the sake of helping anyone who comes by this, I ended up creating my own Extension Method Columns that would convert the column number into a ExcelRange object:

''' <summary>
''' Allows you to reference a column by its numeric index rather than its alphabetic representation
''' </summary>
''' <param name="colNum">The index of the column to reference on in the worksheet.</param>
<System.Runtime.CompilerServices.Extension()> _
Public Function Columns(ByVal wks As ExcelWorksheet, ByVal colNum As Integer) As ExcelRange
    Dim ColName As String = ReturnColumnName(colNum)

    Return wks.Cells(ColName & ":" & ColName)
End Function


''' <summary>
''' Allows you to reference a column by its numeric index rather than its alphabetic representation
''' </summary>
''' <param name="StartColNum">The start col num.</param>
''' <param name="EndColNum">The end col num.</param>
<System.Runtime.CompilerServices.Extension()> _
Public Function Columns(ByVal wks As ExcelWorksheet, ByVal StartColNum As Integer, ByVal EndColNum As Integer) As ExcelRange
    Dim StartColName As String = ReturnColumnName(StartColNum)
    Dim EndColName As String = ReturnColumnName(EndColNum)

    Return wks.Cells(StartColName & ":" & EndColName)
End Function



Private Function ReturnColumnName(ByVal colNum As Integer) As String
    Dim d As Integer
    Dim m As Integer
    Dim Name As String

    d = colNum
    Name = ""

    Do While (d > 0)
        m = (d - 1) Mod 26
        Name = Chr(65 + m) + Name
        d = Int((d - m) / 26)
    Loop

    Return Name
End Function

Answer:

I re-wrote the answer given by @John Bustos in c# and then realised I wanted to work with the columns themselves rather than a cell range. John’s method has been renamed ‘GetColumnCells’ in the code below.

public static List<ExcelColumn> GetColumns(ExcelWorksheet wks, int startColNum, int endColNum) {
    int d = startColNum;
    List<ExcelColumn> cols = new List<ExcelColumn>();

    while (d <= endColNum) {
        cols.Add(wks.Column(d));
        d++;
    }

    return cols;
}

public static ExcelRange GetColumnCells(ExcelWorksheet wks, int startColNum, int endColNum) {
    string startColName = GetColumnName(startColNum);
    string endColName = GetColumnName(endColNum);

    return wks.Cells[startColName + ":" + endColName];
}

public static string GetColumnName(int colNum) {
    int d, m;
    string name = String.Empty;

    d = colNum;
    while (d > 0) {
        m = (d - 1) % 26;
        name = ((char)(65 + m)) + name;
        d = (d - m) / 26;
    }

    return name;
}