T4 POCO. Foreign Key Relationships (List<T> or T?)

Question

I created a T4 template for our POCO objects using SMO to grab the object details from SQL Server. Right now I'm trying to determine how to determine the datatype of the navigation properties. My main issue is how to determine if it should be T or List<T>.

I'm not using EF or Linq to SQL.

Any ideas on what I should be checking to accurately determine the datatype?

Answer 1

What I was looking for is a way to determine the cardinality of a foreign key. I believe it can be done by checking the uniqueness of the primary key column(s), however, we've opted to hard code the navigation properties ourselves without having to worry about this as well as a auto-generating a name for the property.

Answer 2

Depending on which version of SQL you're using, you can use the INFORMATION_SCHEMA to get just about everything you need to build out your POCOs. The following is from http://searchcode.com/codesearch/view/15361587. It lists all tables and columns along with many attributes including whether the column is a foreign key.

SELECT 
--TBL.TABLE_SCHEMA,
TBL.TABLE_TYPE, 
COL.TABLE_NAME,
COL.ORDINAL_POSITION,
COL.COLUMN_NAME,
COL.DATA_TYPE,
COL.IS_NULLABLE,
ISNULL(COL.CHARACTER_MAXIMUM_LENGTH,-1) AS MAXIMUM_LENGTH,
--COL.TABLE_CATALOG,
(CASE KEYUSG.CONSTRAINT_TYPE WHEN 'PRIMARY KEY' THEN 'YES' ELSE 'NO' END) PRIMARY_KEY,
(CASE KEYUSG.CONSTRAINT_TYPE WHEN 'FOREIGN KEY' THEN 'YES' ELSE 'NO' END) FOREIGN_KEY,
FK.FOREIGN_TALBE,
FK.FOREIGN_COLUMN,
KEYUSG.CONSTRAINT_NAME
FROM
INFORMATION_SCHEMA.COLUMNS COL
JOIN
INFORMATION_SCHEMA.TABLES TBL
ON
COL.TABLE_NAME=TBL.TABLE_NAME 

    LEFT JOIN
    (
    SELECT 
    USG.CONSTRAINT_NAME,
    USG.TABLE_NAME,
    USG.COLUMN_NAME,
    CONST.CONSTRAINT_TYPE
     FROM
    INFORMATION_SCHEMA.KEY_COLUMN_USAGE USG
    JOIN
    INFORMATION_SCHEMA.TABLE_CONSTRAINTS CONST
    ON
    USG.TABLE_NAME=CONST.TABLE_NAME
    AND
    USG.CONSTRAINT_NAME = CONST.CONSTRAINT_NAME
    ) 
    AS KEYUSG
ON
COL.TABLE_NAME=KEYUSG.TABLE_NAME
AND
COL.COLUMN_NAME=KEYUSG.COLUMN_NAME

---FOREIGHTKEYS
    LEFT OUTER JOIN
    (
    SELECT 
    USAGE.TABLE_NAME,
    USAGE.COLUMN_NAME,
    UNI_USAGE.TABLE_NAME FOREIGN_TALBE,
    UNI_USAGE.COLUMN_NAME FOREIGN_COLUMN,
    CONST.CONSTRAINT_NAME,
    UNIQUE_CONSTRAINT_NAME
    FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS CONST
    JOIN
    INFORMATION_SCHEMA.KEY_COLUMN_USAGE USAGE
    ON
    USAGE.CONSTRAINT_NAME=CONST.CONSTRAINT_NAME 
    JOIN
    INFORMATION_SCHEMA.KEY_COLUMN_USAGE UNI_USAGE
    ON
    UNI_USAGE.CONSTRAINT_NAME=CONST.UNIQUE_CONSTRAINT_NAME 
    ) 
    AS FK
ON
FK.TABLE_NAME=COL.TABLE_NAME 
AND
FK.COLUMN_NAME = COL.COLUMN_NAME
AND 
KEYUSG.CONSTRAINT_NAME=FK.CONSTRAINT_NAME