StrataFrame Forum » StrataFrame Application Framework - V1 » Business Objects and Data Access (How do I?) » Generic Nullable Gives Compiler Error

Generic Nullable Gives Compiler Error

Richard Keller — Wed, 03 Jan 2007 08:51:38 GMT

I used the Customize Property of the Business Object Mapper to try and set the properties of a Null Field. Here is the error that I get:

Error 2 Type argument 'String' does not satisfy the 'Structure' constraint for type parameter 'T'

RE: Generic Nullable Gives Compiler Error

StrataFrame Team — Wed, 03 Jan 2007 08:51:38 GMT

That's almost correct... the Use Nullable Generic option can only be used with value types that are not nullable (structures, integers, doubles, datetimes, etc.). The System.String data type is a reference type, but it still cannot be cast to DBNull.Value. So, instead of using the Nullable Generic option, you'll most likely need to use the "Return Alternate On Null" option, which returns an alternate value if a Null value is encountered. So, the replacement value would most likely be Nothing (or null for C#).

RE: Generic Nullable Gives Compiler Error

Richard Keller — Wed, 03 Jan 2007 04:53:21 GMT

I think I figured it out. The database column was a string value so that the Generic Nullable is not needed and the application "should" be able to handle because you can set the String to Null without the NUllable Call.

Thanks,

Richard