Cannot specify /main if building a module or library (CS2017

[omayer]

Error Returned - Cannot specify /main if building a module or library (CS2017), when i changed console application to Class library on Output Type

Ranorex .3.1
module library
steps:
Project > project options > Application > Output Type = switch from console application to Class library > error returned when compile

[omayer]

problem resolved by deleting startup object then changed output type = class library