Question

Within a WCF web service I make a query on a ORACLE 11g database and I use entity framework as model. The target field is of type Numeric, while in the entity framework is Int64.

When I try to update the field I get the following exception: The specified cast from a materialized ‘System.Decimal’ type to the ‘System.Int64’ type is not valid.
The method generating the error is below, in particular for the line within the else statement: result = _context.ExecuteStoreQuery(query).FirstOrDefault();

public string GetDatabaseTimestamp(Type timestampFieldType, string query)
{
    object result;

    if (timestampFieldType == typeof(string))
    {
        result = _context.ExecuteStoreQuery<string>(query).FirstOrDefault();
    }
    else
    {
        result = _context.ExecuteStoreQuery<long>(query).FirstOrDefault();
    }

    return result.ToString();
}

Would it be possible to define at the EF level a converter or something similar? The option of changing the Database is not feasible, therefore I have to edit code.

Answer 1

In The EF I already changed the type into decimal. Problem is that the query was executed directly on the Oracle database and this was generating the exception.

I solved the issue by using attributes for the target entity and changed the method into:

public string GetDatabaseTimestamp(Type timestampFieldType, string query) 
{ 
 object result; 

if (timestampFieldType == typeof(string)) 
{ 
  result = _context.ExecuteStoreQuery<string>(query).FirstOrDefault(); 
} 
else if (timestampFieldType == typeof(decimal)) 
{ 
  result = _context.ExecuteStoreQuery<decimal>(query).FirstOrDefault(); 
} 
else 
{  
  result = _context.ExecuteStoreQuery<long>(query).FirstOrDefault(); 
} 

return result.ToString(); 
} 

In this way the passed timestampFieldType is of type decimal and the proper cast is selected. This issue is due to different data types used for similar fields (as example Update fields) in the Oracle DB (legacy database).