Switch datasource using IF statement in Power Query

[AlexHeinze]

I have a report with 2 datasources.

One datasource gets the XML from a file (Source = Xml.Tables(File.Contents(.......):

The second datasource gets a similar XML from an API (Source = Xml.Tables(Web.Contents(.......):

My report has a parameter "Datasource", which is then utilized in Power Query to select file or API datasource:

let
SourceSelection = DataSource,
// Select the sources based on the parameter value
Source = if SourceSelection="API Broadcast" then #"_Get XML from API Broadcast" else #"_Get XML from File"
in
Source

When the parameter is set to file, the returned datasource is correct (column type=table):

However when I set it to API, the returned datasource is wrong (column type=alpha):

Any idea what's wrong here?

[WanderingBI]

I would first check if the problem really comes from the IF statement by simplifying to this first and checking the output:

let
Source =  #"_Get XML from File"
in
Source

This step seems redundant (assigning the parameter to a new variable):

SourceSelection = DataSource,

[AlexHeinze]

Thanks! I had tried this already, referencing the datasource worked for both the API and XML. Here's an example:

let
Source1 = #"_Get XML from API Broadcast",
Source2 = #"_Get XML from File",
// This one works
// Source = Source1
// This one does not work
Source = if (1=1) then Source1 else Source2

in
Source

With the inverted condition and swapped Source 1/2 it doesn't work either. Very strange.

[WanderingBI]

That is indeed very strange and does not conform with my understanding of the evaluation model.

Maybe isolating Source1 and Source2 declaration from the if statement by putting the if into another let/in environment could help:

let
Source1 = #"_Get XML from API Broadcast",
Source2 = #"_Get XML from File",

getData = (choice as text) => 
let
 source = if choice = "api" then Source1 else if choice = "file" then Source2 else null
in
 source

Source = getData("api")

[AlexHeinze]

Thanks for looking into this, @WanderingBI . I had to tweak the code slightly...

let
Source1 = #"_Get XML from API Broadcast",
Source2 = #"_Get XML from File",

getData = (choice as text) => 
let
 funcsource = if choice = "api" then Source1 else if choice = "file" then Source2 else null
in 
 funcsource,

Source = getData ("api")

in

Source

...unfortunately the result for "api" is still broken (while it still works for "file":

[WanderingBI]

Wish I could do more than guessing.

When assuming that the issue is only that the column "Table" is of data type any instead of table and this messes with the software receiving the query output (Power BI), would maybe setting the column type to table manually do any good?

let
Source1 = #"_Get XML from API Broadcast",
Source2 = #"_Get XML from File",

getData = (choice as text) => 
let
 funcsource = if choice = "api" then Source1 else if choice = "file" then Source2 else null
in 
 funcsource,

Source = getData ("api"),
SourceAdjustColumnType = Value.ReplaceType(Source, type table [Table = Table.Type])

in

SourceAdjustColumnType

[AlexHeinze · Accepted solution]

I finally solved it by not referencing the existing sources, instead I put it all in the same place:

let
    // Get data from API
    SourceAPI = Xml.Tables(Web.Contents(GatewayURL)),
    
    // Get data from file
    SourceFile = Xml.Tables(File.Contents(SavedScheduleXML)),
    
    // Select the sources based on the parameter value
    Source = if DataSource="API Broadcast" then SourceAPI else SourceFile,
.......