Unable to load file or assembly xxxx. The system cannot find the file specified.
For example, the file or assembly "System.Threading.Tasks.Extensions, Version=4.2.0.1, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51" or one of its dependencies could not be loaded. The system can not find the file specified.
Solutions to this type of problem:
The bll file of the corresponding assembly is missing in the bin folder. You can copy it from the package folder and add it.
However, after closing the solution project and reopening it, this error will still be reported. The solution is:
Include the bll file in the bin folder into the project.