how to get the data type of a field of a table in a database(Oracle and SqlServer)

Question

Hi all,
while doing programming in asp.net 3.5 using c#,i am stuck with a problem that how we can explicitly and dynamically know the datatype of a field of a table in a database ,and i want to store the datatype in a variable.In the method that i want to define i will pass the connection string,table name and field name,and in return the method will give me the datatype ?
plz explain for Oracle and SQL Server database.
Thanks