/// <summary>
/// Return the unique instance of the ColumnConverter class.
///
/// Author : Lilian DAMIENS
/// Date : January 2021
/// </summary>
/// <returns></returns>
private static ColumnConverter GetInstance()
{
if (_instance == null)
{
_instance = new ColumnConverter();
}
return(_instance);
}
/// <summary>
/// Return the column's letters throught the index of this one.
///
/// Author : Lilian
/// Date : January 2021
/// </summary>
/// <param name="columnIndex"></param>
public static string Get(int columnIndex)
{
ColumnConverter instance = GetInstance();
if (instance.indexToColumn.ContainsKey(columnIndex))
{
return(instance.indexToColumn[columnIndex]);
}
int dividend = columnIndex;
string columnName = String.Empty;
int modulo;
while (dividend > 0)
{
modulo = (dividend - 1) % 26;
columnName = Convert.ToChar(65 + modulo).ToString() + columnName;
dividend = (int)((dividend - modulo) / 26);
}
instance.indexToColumn.Add(columnIndex, columnName);
return(columnName);
}
/// <summary>
/// Return the column's index throught the letters of this one.
///
/// Author : Lilian
/// Date : January 2021
/// </summary>
/// <param name="columnName"></param>
/// <returns></returns>
public static int Get(string columnName)
{
if (String.IsNullOrEmpty(columnName))
{
throw new ConvertColumnException($"Column's name is null or empty.");
}
ColumnConverter instance = GetInstance();
if (instance.columnToIndex.ContainsKey(columnName))
{
return(instance.columnToIndex[columnName]);
}
columnName = columnName.ToUpperInvariant();
int index = 0;
foreach (char letter in columnName)
{
index *= 26;
index += (letter - 'A' + 1);
}
instance.columnToIndex.Add(columnName, index);
return(index);
}
