[c#] What size do you use for varchar(MAX) in your parameter declaration?

I normally set my column size when creating a parameter in ADO.NET

But what size do I use if the column is VARCHAR(MAX)?

cmd.Parameters.Add("@blah", SqlDbType.VarChar, ?????).Value = blah;

For those of us who did not see -1 by Michal Chaniewski, the complete line of code:

cmd.Parameters.Add("@blah",SqlDbType.VarChar,-1).Value = "some large text";

The maximum SqlDbType.VarChar size is 2147483647.

If you would use a generic oledb connection instead of sql, I found here there is also a LongVarChar datatype. Its max size is 2147483647.

cmd.Parameters.Add("@blah", OleDbType.LongVarChar, -1).Value = "very big string";

If you do something like this:

    cmd.Parameters.Add("@blah",SqlDbType.VarChar).Value = "some large text";

size will be taken from "some large text".Length

This can be problematic when it's an output parameter, you get back no more characters then you put as input.

You do not need to pass the size parameter, just declare Varchar already understands that it is MAX like:

cmd.Parameters.Add("@blah",SqlDbType.VarChar).Value = "some large text";