The type or namespace name 'HttpClient' could not be found (are you missing a using directive or an assembly reference?)

The type or namespace name 'HttpRequestMessage' could not be found (are you missing a using directive or an assembly reference?)

The type or namespace name 'HttpClient' could not be found (are you missing a using directive or an assembly reference?)

The type or namespace name 'HttpRequestMessage' could not be found (are you missing a using directive or an assembly reference?)

The type or namespace name 'HttpClient' could not be found (are you missing a using directive or an assembly reference?)

The type or namespace name 'HttpResponseMessage' could not be found (are you missing a using directive or an assembly reference?)

The type or namespace name 'HttpClient' could not be found (are you missing a using directive or an assembly reference?)

'Task' does not contain a definition for 'CompletedTask'

'Task' does not contain a definition for 'CompletedTask'