title: SqlDataReader Error: there is not converion between <null> and 'decimal'
body: <p>I'm working on a C# Desktop App and have a quetion about how to retrieve a value from a database using SqlDataReader.
  When the value is a varchar in the table I save that value in an entity using this:</p>
  
  <pre><code>if (dr.HasRows){
      while (dr.Read()){
      Empleado dato = new Empleado();
      dato.DUIEmp = dr.IsDBNull(0) ? "No Info" : dr.GetString(0);
      ...
  </code></pre>
  
  <p>but I don't know how to retrive a decimal value from the database, for the time being I' using this but doesn't work:</p>
  
  <pre><code>dato.Salario = dr.IsDBNull(4) ? (decimal?)null : Convert.ToDecimal(dr.GetDecimal(4)); 
  </code></pre>
  
  <p>And also have the same problem with the Date value</p>
  
  <pre><code>dato.FechaIngreso = dr.IsDBNull(6) ? "No Info" : dr.GetDateTime(6);
  </code></pre>
  
  <p>Could you please help me and tell me how am I suposse to retrieve those type of data using SqlDatareader please?</p>