You will often find this error when converting IDataReader to POCO. There are 2 resolutions here –
if you are using Automapper 4.0 or above, check MSBuild probably have deleted Automapper.Net4.dll in bin folder, if it is, restore it.
Second, IDataReader is unsupported from Autoamapper. you can use below 4.0 (or 3.1.1), which supports IDataReade, unless you are not using specific version features.