Count e-mail addresses

[MathildaBackman]

I have a table that contains different SharePoint sites.
I have a column called Group.Owners where I have the e-mail address to the owner/owners of that site.
There can be none, one or multiple e-mail addresses in that column. And there are of course different values on each row.
The e-mail addresses all have @ and if there are more than one, they are separeted by a semicolon. 
Like this: person.1@domainone.com; person.2@domaintwo.com; person.33@dom.com

I want to, in the easiest way, count the number of e-mailaddresses on each row.
I thought the easiest way was to count how many times @ appears in that column on each row. But I cant figure out how to do this.

I need help! 

[ZhangKun]

Add a custom column，use following code:

List.Count(Text.PositionOf([Group.Owners], "@", Occurrence.All))

[MathildaBackman]

Oh, great solution, but I get this error:

Expression.Error: We cannot convert the value null to type Text.
Details:
    Value=
    Type=[Type]

[ZhangKun · Accepted solution]

Because some cell is null in Group.Owners column, you can use following code:

List.Count(Text.PositionOf([Group.Owners] ?? "", "@", Occurrence.All))

[Papermain]

I can see the ?? "" replaces the null values with empty text. Is there any documentation available about what the ?? exactly does and if there are other options as well? I cannot find anything and was not aware of this functionality

[ZhangKun]

you search "Coalesce" in this pageOperator behavior 

[MathildaBackman]

Works well no. Just needed to click "Don't summerize" when I added the values from that column in my table.

Thank you for the code and the help.