public IEnumerable<string> CheckColumns(IEnumerable<string> columnNames)
{
var result = new List<string>();
foreach (var columnName in columnNames) {
var resolved = ResolveColumnName(columnName);
if (resolved == null)
throw new InvalidOperationException(String.Format("Column '{0}' not found in table.", columnName));
result.Add(resolved);
}
return result.ToArray();
}