value of userid from table

It looks like you're trying to retrieve the value of userid from the Users table. However, there are a few issues with your code:

1. You're setting cmd.CommandType to CommandType.Text, but you're not providing a SQL query. Instead, you're just specifying the table name Users.
2. You're calling ExecuteNonQuery() which is used to execute a query that doesn't return any data. But you want to retrieve the value of userid, so you should use ExecuteScalar() or ExecuteReader() instead.
3. You're trying to convert the result of ExecuteScalar() to an integer, but you haven't specified which column you want to retrieve.

Here's an updated version of your code that should work:

SqlCommand cmd = new SqlCommand("SELECT userid FROM Users", con);
cmd.CommandType = CommandType.Text;
con.Open();
object result = cmd.ExecuteScalar();
int userid = Convert.ToInt32(result);

In this code, we're specifying a SQL query that selects the userid column from the Users table. We're then calling ExecuteScalar() to retrieve the first column of the first row of the result set. Finally, we're converting the result to an integer using Convert.ToInt32().

Note that if your table has multiple rows, this code will only retrieve the userid value from the first row. If you want to retrieve all the userid values, you'll need to use ExecuteReader() instead.