F# - printfn Guid

Question

I have following printing example in F#

for row in data.Rows do 
     printfn "Example: (%s)" row.A

But I received this error

Script1.fsx(15,67): error FS0001: This expression was expected to have type string but here has type Guid

I didn't find any example of printing of Guid type. I tried apply ToString() method to row.A but it is not working as well

Answer 1

There are two options here:

for row in data.Rows do 
     printfn "Example: (%s)" (row.A.ToString())

or

for row in data.Rows do 
     printfn "Example: (%A)" row.A

Here the %A can be used for any type and the compiler will automatically print it for you

Answer 2

You can use %A for a Guid, like this:

printfn "Example: (%A)" row.A

When using %s , the type must be a string.

The MSDN Documentation has more information about which format type to use and how it behaves.

Answer 3

In addition to the answers already given, it's worth noting that Guid also supports an overload of ToString , giving you the option to control how the GUID string is formatted.

You could, for example, write it out like this:

printfn "Example: (%s)" (row.A.ToString "n")

if you want to omit the hyphens ( Example: (78e6fb89dc5045988d445c4d8aef4e28) ).

Or you could use stringf for this, if you want an alternative with pipes instead of parentheses:

row.A |> stringf "n" |> printfn "Example: (%s)"

or if you don't need the formatting option:

row.A |> string |> printfn "Example: (%s)"