Errors: Could not be found (are you missing a using directive or an assembly reference)

[Jamster3000]

I know this repository is old but it's helping me a little in the right direction. I'm working on something to use eBay with a program and I myself have come accross several error that I am not yet abel to fix (which would be better mentioned else where in the hopes that someone will assist).

Errors

Severity	Code	Description	Project	File	Line	Suppression State	Details
Error	CS0246	The type or namespace name 'DetailLevelCodeTypeCollection' could not be found (are you missing a using directive or an assembly reference?)	EbayConsole	[filepath]	22	Active	

Error	CS0246	The type or namespace name 'eBayAPIInterfaceService' could not be found (are you missing a using directive or an assembly reference?)	EbayConsole	[filepath]	15	Active	

Error	CS0246	The type or namespace name 'FeatureIDCodeTypeCollection' could not be found (are you missing a using directive or an assembly reference?)	EbayConsole	[filepath]	81	Active	

Error	CS0246	The type or namespace name 'StringCollection' could not be found (are you missing a using directive or an assembly reference?)	EbayConsole	[filepath]	55	Active	

Really would appreciate help on the matters if possible.