title: Entity Framework exception for parameters that have 'allow nulls' enabled
body: <p>I am adding a new register into the SQL Server database using Entity Framework like this:</p>
  <pre><code>var configSlot = new DeviceConfig_DB
                       {
                           ID_DeviceConfig = 95,
                           ConfigName = configName,
                           ParamName = &quot;Param1&quot;,
                           ParamValue = &quot;1000&quot;,
                           ToolName = null,
                           ToolValue = null,
                       };
  </code></pre>
  <p>It returns a validation error exception because of <code>ToolName</code> and <code>ToolValue</code> fields, and only are accepted if I set a string value (that fields are <code>nvarchar</code>).</p>
  <p>If I insert a new register using a SQL Server Management Studio query, it is accepted even if I don't provide those fields. They do have the 'allow nulls' option.</p>
  <pre><code>INSERT INTO [dbo].[DeviceConfig_DB] ([ID_DeviceConfig], [ConfigName], [ParamName], [ParamValue])
  VALUES (96, 'test', 'Param1', '1000')
  </code></pre>
  <p>How can I insert a new register with Entity Framework with null values for those fields?</p>
  <p>EDIT:
  Here is the DeviceConfig_DB class</p>
  <pre><code>  public partial class DeviceConfig_DB
      {
          public int ID_DeviceConfig { get; set; }
          public Nullable&lt;int&gt; ID_PhysicalDevice { get; set; }
          public string ConfigName { get; set; }
          public string ParamName { get; set; }
          public string ParamValue { get; set; }
          public string ToolName { get; set; }
          public string ToolValue { get; set; }
      
          public virtual PhysicalDevice_DB PhysicalDevice_DB { get; set; }
      }
  </code></pre>