Unable to connect my MVC web appliaction to Oracle Database using code first method

I am trying to connect my web application to oracle database using code first approach it is not connecting throwing a error message as below Error Code : 0x800700b7 Config Error: There is a duplicate 'oracle.manageddataaccess.client' section defined after googling tried to comment oracle.manageddataaccess.client section in my machine.config file but issue not solved.

My web.config file as follow

<?xml version="1.0"?>
<!--
  For more information on how to configure your ASP.NET application, please visit
  http://go.microsoft.com/fwlink/?LinkId=169433
  -->
<configuration>
  <configSections>
    <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 -->
    <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false"/>
    <section name="oracle.manageddataaccess.client" type="OracleInternal.Common.ODPMSectionHandler, Oracle.ManagedDataAccess, Version=4.121.2.0, Culture=neutral, PublicKeyToken=89b483f429c47342"/>
  </configSections>
  <appSettings>
    <add key="webpages:Version" value="3.0.0.0"/>
    <add key="webpages:Enabled" value="false"/>
    <add key="PreserveLoginUrl" value="true"/>
    <add key="ClientValidationEnabled" value="true"/>
    <add key="UnobtrusiveJavaScriptEnabled" value="true"/>
  </appSettings>

  <system.web>
    <compilation debug="true" targetFramework="4.5"/>
    <httpRuntime targetFramework="4.5"/>
    <pages>
      <namespaces>
        <add namespace="System.Web.Helpers"/>
        <add namespace="System.Web.Mvc"/>
        <add namespace="System.Web.Mvc.Ajax"/>
        <add namespace="System.Web.Mvc.Html"/>
        <add namespace="System.Web.Routing"/>
        <add namespace="System.Web.WebPages"/>
      </namespaces>
    </pages>
    <httpModules>
      <add name="ApplicationInsightsWebTracking" type="Microsoft.ApplicationInsights.Web.ApplicationInsightsHttpModule, Microsoft.AI.Web"/>
    </httpModules>
  </system.web>
  <system.webServer>
    <validation validateIntegratedModeConfiguration="false"/>
    <handlers>
      <remove name="ExtensionlessUrlHandler-Integrated-4.0"/>
      <remove name="OPTIONSVerbHandler"/>
      <remove name="TRACEVerbHandler"/>
      <add name="ExtensionlessUrlHandler-Integrated-4.0" path="*." verb="*" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0"/>
    </handlers>
    <modules>
      <remove name="ApplicationInsightsWebTracking"/>
      <add name="ApplicationInsightsWebTracking" type="Microsoft.ApplicationInsights.Web.ApplicationInsightsHttpModule, Microsoft.AI.Web" preCondition="managedHandler"/>
    </modules>
  </system.webServer>
  <runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="Newtonsoft.Json" culture="neutral" publicKeyToken="30ad4fe6b2a6aeed"/>
        <bindingRedirect oldVersion="0.0.0.0-6.0.0.0" newVersion="6.0.0.0"/>
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Helpers" publicKeyToken="31bf3856ad364e35"/>
        <bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0"/>
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Mvc" publicKeyToken="31bf3856ad364e35"/>
        <bindingRedirect oldVersion="1.0.0.0-5.2.0.0" newVersion="5.2.0.0"/>
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Optimization" publicKeyToken="31bf3856ad364e35"/>
        <bindingRedirect oldVersion="1.0.0.0-1.1.0.0" newVersion="1.1.0.0"/>
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.WebPages" publicKeyToken="31bf3856ad364e35"/>
        <bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0"/>
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="WebGrease" publicKeyToken="31bf3856ad364e35"/>
        <bindingRedirect oldVersion="0.0.0.0-1.5.2.14234" newVersion="1.5.2.14234"/>
      </dependentAssembly>
      <dependentAssembly>
        <publisherPolicy apply="no"/>
        <assemblyIdentity name="Oracle.ManagedDataAccess" publicKeyToken="89b483f429c47342" culture="neutral"/>
      </dependentAssembly>
    </assemblyBinding>
  </runtime>
  <system.codedom>
    <compilers>
      <compiler language="c#;cs;csharp" extension=".cs" type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.CSharpCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" warningLevel="4" compilerOptions="/langversion:6 /nowarn:1659;1699;1701"/>
      <compiler language="vb;vbs;visualbasic;vbscript" extension=".vb" type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.VBCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" warningLevel="4" compilerOptions="/langversion:14 /nowarn:41008 /define:_MYTYPE=\&quot;Web\&quot; /optionInfer+"/>
    </compilers>
  </system.codedom>
  <entityFramework>
    <!--<defaultConnectionFactory type="System.Data.Entity.Infrastructure.SqlConnectionFactory, EntityFramework"/>-->
    <providers>
      <provider invariantName="Oracle.ManagedDataAccess.Client" type="Oracle.ManagedDataAccess.EntityFramework.EFOracleProviderServices, Oracle.ManagedDataAccess.EntityFramework, Version=6.122.1.0, Culture=neutral, PublicKeyToken=89b483f429c47342"/>
    </providers>
  </entityFramework>
  <system.data>
    <DbProviderFactories>
      <!--<add name="Oracle Data Provider for .NET" invariant="Oracle.ManagedDataAccess.Client" description="Oracle Data Provider for .NET" type="Oracle.ManagedDataAccess.Client.OracleClientFactory, Oracle.ManagedDataAccess, Version=4.121.1.0, Culture=neutral, PublicKeyToken=89b483f429c47342" />-->
      <remove invariant="Oracle.ManagedDataAccess.Client"/>
      <add name="ODP.NET, Managed Driver" invariant="Oracle.ManagedDataAccess.Client" description="Oracle Data Provider for .NET, Managed Driver" type="Oracle.ManagedDataAccess.Client.OracleClientFactory, Oracle.ManagedDataAccess, Version=4.121.2.0, Culture=neutral, PublicKeyToken=89b483f429c47342"/>
    </DbProviderFactories>
  </system.data>
  <oracle.manageddataaccess.client>
    <version number="*">
      <dataSources>
        <dataSource alias="*userid*DBSource" descriptor="(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=*hostname given*)(PORT=1525))(CONNECT_DATA=(SERVICE_NAME=*servicename given*))) " />
        <!--<dataSource alias="SampleDataSource" descriptor="(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=localhost)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=ORCL))) "/>-->
      </dataSources>
    </version>
  </oracle.manageddataaccess.client>
  <connectionStrings>
    <add name="OracleDbContext" providerName="Oracle.ManagedDataAccess.Client" connectionString="User Id=oracle_user;Password=oracle_user_password;Data Source=oracle"/>
    <add name="WAT_DBContext" providerName="Oracle.ManagedDataAccess.Client" connectionString="User Id=*userid*;Password=*psw*;DATA SOURCE=(DESCRIPTION =(ADDRESS = (PROTOCOL = TCP)(HOST = *hostname given*)(PORT = 1525))(CONNECT_DATA =(SERVICE_NAME = *servicename given*)));USER ID=*user id*"/>
  </connectionStrings>
</configuration>

I am using Oracleclient 11g ,Entity framework 6.0.0 and oracle managed dataaccess 12c from nugnet package version. for the same code my console application connected to oracle database.I am newbie to .net so i need a help to proceed further. Thanks in advance, niyut

Setting up Oracle with Visual Studio can be tricky. If you have an Oracle Home installed, the driver versions can, I think, get in conflict with your oracle.manageddataaccess.client Nuget-installed version.

I found that I needed to uninstall the Oracle Home. What works for me is to only have the Oracle Developer Tools for Visual Studio installed on your machine, and then install the Oracle.ManagedDataAccess nuget package into any projects that need to connect to Oracle. I would uninstall the Oracle Home if you have one (and if you don't need to keep it).

I would avoid editing machine.config directly. You should be able to connect to Oracle using the Nuget package and the "Dev Tools for Visual Studio" alone, this works for me. After that it can be tricky to configure the connection but you should get past the duplicate entry error. Good luck!