Add File Name and Modified Date Column in Power Query M

Adds the source file's name and last-modified date as columns, when combining multiple files from a folder.

File HandlingIntermediatefolderfilenamemodified datemetadata

Power Query M code

let
    Source = Folder.Files("C:\Data\SalesFiles"),
    AddedData = Table.AddColumn(Source, "Data", each Csv.Document([Content], [Delimiter = ","])),
    ExpandedData = Table.ExpandTableColumn(AddedData, "Data", {"Column1", "Column2"}),
    KeptMetadata = Table.SelectColumns(ExpandedData, {"Name", "Date modified", "Column1", "Column2"})
in
    KeptMetadata

Notes

Rename Name and Date modified to SourceFile and SourceModified if you want clearer column names.

Requirements

A folder of files being combined, where you also need to know which file each row came from.

How to use this snippet

In Power BI Desktop, choose Transform data to open Power Query, then open the Advanced Editor on a query (or start from a blank query).
Paste the snippet and replace the placeholder names (tables, columns, file paths) with your own. Check the requirements above first.
Run it through the Power Query M Formatter to tidy the layout.

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