There was a problem running the selected code generator : 'Package restore Failed'

Question

Some weeks before i encountered similar problem of scaffolding error and got the solution. What am i trying is controllers>add>new scaffolded item >MVC controller with views , using entity framework

Link:-

Error running selected code generator The database provider attempted to register an implementation of 'IRelationTypeMappingSource'

But the thing is I'm facing that problem again.

My cproj file :

<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
    <TargetFramework>netcoreapp3.1</TargetFramework>
  </PropertyGroup>

  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|AnyCPU'">
    <Prefer32Bit>false</Prefer32Bit>
  </PropertyGroup>

  <ItemGroup>
    <Compile Remove="Migrations\20200625063143_user_table_added_for_access_control.cs" />
    <Compile Remove="Migrations\20200625063143_user_table_added_for_access_control.Designer.cs" />
    <Compile Remove="Migrations\20200625070609_test.cs" />
    <Compile Remove="Migrations\20200625070609_test.Designer.cs" />
    <Compile Remove="Migrations\20200701100225_datatype_changed_to_long_of_assetno_in_both_table.cs" />
    <Compile Remove="Migrations\20200701100225_datatype_changed_to_long_of_assetno_in_both_table.Designer.cs" />
    <Compile Remove="Migrations\20200730114532_hasShiftingRequest_field_added_in_pc.cs" />
    <Compile Remove="Migrations\20200730114532_hasShiftingRequest_field_added_in_pc.Designer.cs" />
    <Compile Remove="Migrations\20200731033230_hasShiftingRequest_field_added_in_pc.cs" />
    <Compile Remove="Migrations\20200731033230_hasShiftingRequest_field_added_in_pc.Designer.cs" />
    <Compile Remove="Migrations\20200917095552_trial.cs" />
    <Compile Remove="Migrations\20200917095552_trial.Designer.cs" />
    <Compile Remove="Migrations\20201208042418_test.cs" />
    <Compile Remove="Migrations\20201208042418_test.Designer.cs" />
    <Compile Remove="Migrations\20201208054030_User_table_mapped_with_laptop_and_desktop.cs" />
    <Compile Remove="Migrations\20201208054030_User_table_mapped_with_laptop_and_desktop.Designer.cs" />
  </ItemGroup>

  <ItemGroup>
    <Content Remove="Views\AssetDataLaptops\Delete.cshtml" />
    <Content Remove="Views\AssetDataPcs\Delete.cshtml" />
    <Content Remove="Views\AssetShiftings\Delete.cshtml" />
    <Content Remove="Views\AssetShiftings\Details.cshtml" />
    <Content Remove="Views\AssetShiftings\Edit.cshtml" />
  </ItemGroup>

  <ItemGroup>
    <PackageReference Include="bootstrap" Version="4.6.0" />
    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="3.1.4" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Relational" Version="3.1.4" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite" Version="3.1.4" />    
    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="3.1.4" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="3.1.4">
      <PrivateAssets>all</PrivateAssets>
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
    </PackageReference>
    <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration" Version="3.1.4" />
    <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="3.1.4" />
    <PackageReference Include="System.DirectoryServices" Version="5.0.0" />
    <PackageReference Include="System.DirectoryServices.AccountManagement" Version="5.0.0" />
    <PackageReference Include="System.Management" Version="5.0.0" />
  </ItemGroup>

  <ItemGroup>
    <Folder Include="LocationReports\" />
  </ItemGroup>
</Project>

Note :-

I have tried....

-clean and rebuild

-updating all packages

-clear nuget cache

-delete .vs folder and open project and clean/rebuild

-disabling offline nuget package source

-add "https://api.nuget.org/v3/index.json" in nuget package sources

-downgraded all package to 3.1.4 and made same version