Asset file "Obj\project.assets.json" is not ". netcoreapp,version=v2.0 "goal. Make sure that the restore is running, and that "netcoreapp2.0" is already included in the project's Targetframeworks.

Project upgrade to core2.1 build success, run successfully, release this error: v2.0 This field is not found in JSON, I do not know why.

Severity Code description project file line suppress status
The error asset file "E:\work\TxJunshishu\Book\Com.Junshishu\Com.Junshishu.Book.Web.Author\obj\project.assets.json" is not ". netcoreapp,version=v2.0 "goal. Make sure that the restore is running, and that "netcoreapp2.0" is already included in the project's Targetframeworks. Com.Junshishu.Book.Web.Author0

{
"Version": 3,
"Targets": {
". netcoreapp,version=v2.1 ": {
"dapper/1.50.4": {
"Type": "Package",
"Dependencies": {
"System.Data.SqlClient": "4.4.0",
"System.Reflection.Emit.Lightweight": "4.3.0",
"System.Reflection.TypeExtensions": "4.4.0"
},
"Compile": {
"Lib/netstandard2.0/dapper.dll": {}
},
"Runtime": {
"Lib/netstandard2.0/dapper.dll": {}
}
},

Asset file "Obj\project.assets.json" is not ". netcoreapp,version=v2.0 "goal. Make sure that the restore is running, and that "netcoreapp2.0" is already included in the project's Targetframeworks.