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Install MySQL Server 8.0.16
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Install Complete MySQL Connector.Net x86 8.0.16
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Install this custom repacked VSIX MySQL Visual Studio
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If after installing MySQL Visual Studio Plugin it shows warning that failed to execute comamnd
devenv /updateconfiguration, then manually execute that command in Developer Command Prompt for Visual Studio 20xx with run as administrator. - 
Run this command
Install-Package EntityFrameworkin Visual Studio Nuget package manager console - 
Manage Nuget Packages > Search Mysql > install Mysql.Data v8.0.16
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Manage Nuget Packages > Search Mysql > install Mysql.Data.Entity v6.10.8
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Manage Nuget Packages > Search Mysql.Data.EntityFramework > install Mysql.Data.EntityFramework v8.0.16
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Comment the following kind of similar code from
Web.configwhich is already added by the project 
<entityFramework>
    <defaultConnectionFactory type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework">
      <parameters>
        <parameter value="mssqllocaldb" />
      </parameters>
    </defaultConnectionFactory>
    <providers>
      <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
    <provider invariantName="MySql.Data.MySqlClient" type="MySql.Data.MySqlClient.MySqlProviderServices, MySql.Data.Entity.EF6, Version=6.10.8.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d">
      </provider><provider invariantName="MySql.Data.MySqlClient" type="MySql.Data.MySqlClient.MySqlProviderServices, MySql.Data.EntityFramework, Version=8.0.16.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d">
      </provider></providers>
</entityFramework>- Add this lines if its not automatically added after 
</runtime>tag inWeb.configand rebuild solution 
  <entityFramework>
    <defaultConnectionFactory type="System.Data.Entity.Infrastructure.SqlConnectionFactory, EntityFramework" />
    <providers>
      <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
      <!--<provider invariantName="MySql.Data.MySqlClient" type="MySql.Data.MySqlClient.MySqlProviderServices, MySql.Data.Entity.EF6, Version=6.10.8.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d">
      </provider>-->
      <provider invariantName="MySql.Data.MySqlClient" type="MySql.Data.MySqlClient.MySqlProviderServices, MySql.Data.EntityFramework, Version=8.0.16.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d">
      </provider>
    </providers>
  </entityFramework>- Comment 
<compilers>inWeb.configas per below 
  <system.codedom>
    <!--<compilers>
      <compiler language="c#;cs;csharp" extension=".cs" type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.CSharpCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" warningLevel="4" compilerOptions="/langversion:default /nowarn:1659;1699;1701" />
      <compiler language="vb;vbs;visualbasic;vbscript" extension=".vb" type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.VBCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" warningLevel="4" compilerOptions="/langversion:default /nowarn:41008 /define:_MYTYPE=\"Web\" /optionInfer+" />
    </compilers>-->
  </system.codedom>- 
Even if doing all the above process some error occurs, then try uninstall nuget packages all the above added and
UnInstall-Package EntityFrameworkuninstall visual studio plugin and connector net. Then rebuild fresh project, and add onlyInstall-Package EntityFrameworkand then add references only Mysql.Data and Mysql.Data.EntityFramework for EF6 and then add the provider xml in web.config as mentioned above and remove the white space between the<provider>and</provider>tags, and rebuild project and finally try to add model. - 
This process is tested and working for .Net Framework 4.7.2 on Visual Studio 2019
 
Thank you