MSDN的帮助是不错，可惜举的例子比较特殊，没有解释如何做模糊查询。
只有这么一句：
SqlMembershipProvider 通过对 usernameToMatch 参数使用 LIKE 子句来执行搜索。LIKE 子句中受 SQL Server 支持的任何通配符都可以在 usernameToMatch 参数值中使用。
查了下LIKE子句，英文的在这里
http://msdn.microsoft.com/en-us/library/aa933232(SQL.80).aspx
| Wildcard character | Description | Example |
|---|---|---|
| % | Any string of zero or more characters. | WHERE title LIKE '%computer%' finds all book titles with the word 'computer' anywhere in the book title. |
| _ (underscore) | Any single character. | WHERE au_fname LIKE '_ean' finds all four-letter first names that end with ean (Dean, Sean, and so on). |
| [ ] | Any single character within the specified range ([a-f]) or set ([abcdef]). | WHERE au_lname LIKE '[C-P]arsen' finds author last names ending with arsen and beginning with any single character between C and P, for example Carsen, Larsen, Karsen, and so on. |
| [^] | Any single character not within the specified range ([^a-f]) or set ([^abcdef]). | WHERE au_lname LIKE 'de[^l]%' all author last names beginning with de and where the following letter is not l. |
简单的说，%就可以做模糊查询了，和sql一样，如果前后字符未知，可以这么做 "%" + name + "%"，这样就可以实现模糊查询了。当然，更复杂的查询也可以通过不同的通配符组合来实现。