Entity Framework Core 5.0 does not support string.Concat with more than 2 args

[vsfeedback]

This issue has been moved from a ticket on Developer Community.

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A Query similar to:

From t In Me.DataStore.qryAbo
Where t.AboAdrKey = 1035
Order By t.AboActive Descending, t.PrdName, t.TypName
Select New With {t.AboKey, t.AboAdrKey, t.AboActive, . PrdName = String.Concat(t.PrdName, " ", t.TypName, If(t.AboTrial, " (Trial)", ""))}

gets translated to

DECLARE @__DataRow_AdrKey_0 int = 1035;
SELECT [q]. [AboKey], [q]. [AboAdrKey], [q]. [AboActive], [q]. [PrdName], [q]. [TypName], CASE WHEN COALESCE([q].[ AboTrial], CAST(0 AS bit)) = CAST(1 AS bit) THEN N' (Trial)'
    ELSE N''
END
FROM [qryAbo] AS [q]
WHERE COALESCE(CASE
    WHEN ([q].[ AboAdrKey] = @__DataRow_AdrKey_0) AND [q]. [AboAdrKey] IS NOT NULL THEN CAST(1 AS bit)
    ELSE CAST(0 AS bit)
END, CAST(0 AS bit)) = CAST(1 AS bit)
ORDER BY [q]. [AboActive] DESC, [q]. [PrdName], [q]. [TypName]

which brings back 6 columns instead of 4.

Is this by design or should System.Concat be supported?

Thank you for feedback.

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Original Comments

May Lei [MSFT] on 12/13/2020, 11:39 PM:

Not sure the area path, please help to reassign if the area path is not correct. Thanks.

Travico Support on 12/15/2020, 05:19 AM:

(private comment, text removed)

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Original Solutions

(no solutions)

[smitpatel]

We are not capturing overloads which takes 3 & 4 strings as args. Easy to add in relational StringMethodTranslator.
(Also consider translating string.Concat (all overaloads for cosmos)

[wmeints]

I'd like to try and fix this one as a first issue. One question though: What do you mean with the string.Concat overloads for cosmos? Do you have the link to the source file for me where these overloads are located?

[smitpatel]

https://docs.microsoft.com/en-us/dotnet/api/system.string.concat?view=net-5.0

[wmeints]

Sorry, I think I wasn't very clear with my question. I'm looking for the class that translates the String.Concat for the CosmosDB provider. In the mean time I was able to locate the one for the relational provider.

efcore/src/EFCore.Relational/Query/Internal/StringMethodTranslator.cs

Line 72 in 0b31650

return _sqlExpressionFactory.Add(

[ajcvickers]

Looks like this didn't make it into the preview 1 branch. It was merged after preview 1 branched, but before branding was updated to preview 2.