Data source type field is empty when trying to add data tables via Add > Other > Database

Data source type field is empty when trying to add data tables via Add > Other > Database

When trying to add data tables via Add - Other - Database, the field "Data Source type" is empty.
This error may bee seen due to an issue in the machine.config file, which can happen when multiple versions of .NET are installed. A possible solution can be the following:

1. Find the machine.config file and make a backup of it in case needed. An example of how the path to the file can look:

• C:\Windows\Microsoft.NET\Framework\v4.0.30319\Config\Machine.Config

2. The block to pay attention to is <DbProviderFactories>, an example of how it can look is below:

<system.data>
  <DbProviderFactories>
    <add name="IBM DB2 for i5/OS .NET Provider" invariant="IBM.Data.DB2.iSeries" description=".NET Framework Data Provider for i5/OS" type="IBM.Data.DB2.iSeries.iDB2Factory, IBM.Data.DB2.iSeries, Version=12.0.0.0, Culture=neutral, PublicKeyToken=9cdb2ebfb1f93a26"/>
    <add name="Microsoft SQL Server Compact Data Provider" invariant="System.Data.SqlServerCe.3.5" description=".NET Framework Data Provider for Microsoft SQL Server Compact" type="System.Data.SqlServerCe.SqlCeProviderFactory, System.Data.SqlServerCe, Version=3.5.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91"/>
  </DbProviderFactories>

  <DbProviderFactories/>

</system.data>

3. In the machine.config file under the Vx.xx folder, look for lines like (note that there are two separate DbProviderFactories nodes, one with data and one empty node):

<system.data>
  ...
 <DbProviderFactories />
</system.data>

4. Delete this line only (the empty DbProviderFactories node):

<DbProviderFactories />

5. Close and save the file. For example, the above example block when modified correctly would look like the following:

<system.data>
  <DbProviderFactories>
    <add name="IBM DB2 for i5/OS .NET Provider" invariant="IBM.Data.DB2.iSeries" description=".NET Framework Data Provider for i5/OS" type="IBM.Data.DB2.iSeries.iDB2Factory, IBM.Data.DB2.iSeries, Version=12.0.0.0, Culture=neutral, PublicKeyToken=9cdb2ebfb1f93a26"/>
    <add name="Microsoft SQL Server Compact Data Provider" invariant="System.Data.SqlServerCe.3.5" description=".NET Framework Data Provider for Microsoft SQL Server Compact" type="System.Data.SqlServerCe.SqlCeProviderFactory, System.Data.SqlServerCe, Version=3.5.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91"/>
  </DbProviderFactories>
</system.data>

https://forums.asp.net/t/1693277.aspx