Translate a column index into an Excel Column Name

Question

Given a columns\' index, how can you get an Excel column name?

The problem is trickier than it sounds because it\'s not just base-26. The columns

Answer 1

Here is my answer in C#, for translating both ways between column index and column name.

/// 

/// Gets the name of a column given the index, as it would appear in Excel.
/// 
/// The zero-based column index number.
/// The name of the column.
/// Column 0 = A, 26 = AA.
public static string GetColumnName(int columnIndex)
{
    if (columnIndex < 0) throw new ArgumentOutOfRangeException("columnIndex", "Column index cannot be negative.");

    var dividend = columnIndex + 1;
    var columnName = string.Empty;

    while (dividend > 0)
    {
        var modulo = (dividend - 1) % 26;
        columnName = Convert.ToChar(65 + modulo) + columnName;
        dividend = (dividend - modulo) / 26;
    }

    return columnName;
}

/// 

/// Gets the zero-based column index given a column name.
/// 
/// The column name.
/// The index of the column.
public static int GetColumnIndex(string columnName)
{
    var index = 0;
    var total = 0;
    for (var i = columnName.Length - 1; i >= 0; i--)
        total += (columnName.ToUpperInvariant()[i] - 64) * (int)Math.Pow(26, index++);

    return total - 1;
}