How to enable ISO frames on a USB-to-CANFD adapter

In the CAN monitor application there is a checkbox to enable the ISO message. How do I enable the same using the API?

Which API are you using?

VCI4

VCINPL2.dll

It is in ISO mode by default and can be disabled in the InitLine function in the .NET API:

   mCanCtl.InitLine(CanOperatingModes.Standard |
      CanOperatingModes.Extended |
      CanOperatingModes.ErrFrame,
      CanExtendedOperatingModes.ExtendedDataLength | CanExtendedOperatingModes.FastDataRate | CanExtendedOperatingModes.NonIsoCanFd,

This is for the ISO conform frame?

Yes. It is enabled by default and it would need to be disabled by using CanExtendedOperatingModes.NonIsoCanFd as shown above.