error MSB3758， error MSB4036 vs2015

I get the following error:

The source file for this compilation can be found at: "C:\Users\yjgao\AppData\Local\Temp\0fc673c5-6bfc-48f2-b864-5be4c0433706.txt" QtGuiApplication1 C:\Users\yjgao\AppData\Local\QtMsBuild\qt_vars.targets 239 Error MSB3758 An error has occurred during compilation. c:\Users\yjgao\AppData\Local\Temp\y2idmamc.0.cs(103,26) : error CS1061: 'System.Collections.Generic.IEnumerable<string>' does not contain a definition for 'ToHashSet' and no extension method 'ToHashSet' accepting a first argument of type 'System.Collections.Generic.IEnumerable<string>' could be found (are you missing a using directive or an assembly reference?)QtGuiApplication1 C:\Users\yjgao\AppData\Local\QtMsBuild\qt_vars.targets 239 Error MSB4036 The "GetVarsFromMakefile" task was not found. Check the following: 1.) The name of the task in the project file is the same as the name of the task class. 2.) The task class is "public" and implements the Microsoft.Build.Framework.ITask interface. 3.) The task is correctly declared with <UsingTask> in the project file, or in the *.tasks files located in the "C:\Program Files (x86)\MSBuild\14.0\bin" directory. QtGuiApplication1 C:\Users\yjgao\AppData\Local\QtMsBuild\qt_vars.targets 239