How do I list user defined types in a SQL Server database?

I need to enumerate all the user defined types created in a SQL Server database with CREATE TYPE, and/or find out whether they have already been defined.

With tables or stored procedures I'd do something like this:

if exists (select * from dbo.sysobjects where name='foobar' and xtype='U')
    drop table foobar

However I can't find the equivalent (or a suitable alternative) for user defined types! I definitely can't see them anywhere in sysobjects.

Can anyone enlighten me?

Types and UDTs don't appear in sys.objects. You should be able to get what you're looking for with the following:

select * from sys.types
where is_user_defined = 1

Although the post is old, I found it useful to use a query similar to this. You may not find some of the formatting useful, but I wanted the fully qualified type name and I wanted to see the columns listed in order. You can just remove all of the SUBSTRING stuff to just get the column name by itself.

SELECT USER_NAME(TYPE.schema_id) + '.' + TYPE.name      AS "Type Name",
       COL.column_id,
       SUBSTRING(CAST(COL.column_id + 100 AS char(3)), 2, 2)  + ': ' + COL.name   AS "Column",
       ST.name                                          AS "Data Type",
       CASE COL.Is_Nullable
       WHEN 1 THEN ''
       ELSE        'NOT NULL' 
       END                                              AS "Nullable",
       COL.max_length                                   AS "Length",
       COL.[precision]                                  AS "Precision",
       COL.scale                                        AS "Scale",
       ST.collation                                     AS "Collation"
FROM sys.table_types TYPE
JOIN sys.columns     COL
    ON TYPE.type_table_object_id = COL.object_id
JOIN sys.systypes AS ST  
    ON ST.xtype = COL.system_type_id
where TYPE.is_user_defined = 1
ORDER BY "Type Name",
         COL.column_id