Entity Framework - how to get database column datatype from metadata

Question

Is there a way to get the database column DataType length information given a table's EntityType?

Example SQL (SQL Server) that you can run to see precisely what information I am looking for:

select 
    sys.tables.name as 'Table Name', 
    sys.columns.name as 'Column Name', 
    sys.systypes.name as 'DataType', 
    sys.columns.max_length as 'Max Length', 
    sys.columns.precision as 'Precision'
from 
    sys.columns, sys.systypes, sys.tables
where 
    sys.columns.system_type_id = sys.systypes.xtype 
    and sys.systypes.name <> 'sysname' 
    and sys.tables.type = 'U' 
    and sys.tables.name <> 'sysdiagrams'
    and sys.columns.object_id=sys.tables.object_id
order by 
    sys.tables.name, sys.columns.column_id;

The last 3 columns contain the data that I would like to have access to because I'm generating some documentation. One example reason for the documentation is: Entity Framework will throw an Exception by default if a string is set on a property that can't support it's length. A developer without access to the database metadata has a challenge with the discoverability of length requirements in this case.

Thanks, Aaron

Answer 1

Unfortunately no.

Even if that information is correctly captured in the SSDL (i.e. the Storage Schema Definition language) there is no public API in EF to go from C-Space (conceptual model) property to S-Space (storage model) column.

If your model is simple you can perhaps infer that information, using the EF metadata workspace and some simple heuristics, but once things get even a little complicated, those heuristics will break down.

Your only option at that point is to write code to interpret MSL (mapping or CS-Space) files, and use that in conjunction with the MetadataWorkspace to go from C-Space to S-Space.

EDIT: as pointed out by KristoferA you often have the attribute on the C-Space property, so you can go to directly to that. Unfortunately that is not always the case, and often it gets out of sync with the database.