Difference between Add and AddWithValue for Command Parameters in .Net

There is no difference in terms of functionality.

For more details Refer

http://jwcooney.com/2012/09/10/asp-net-choosing-parameters-add-or-parameters-addwithvalue/

cmd.Parameters.Add("@FirstName",SqlDbType.VarChar).Value =  txtFirstName.Text.Trim();

This method requires that you specify the DbType. This helps to reduce the likelihood of such errors.

cmd.Parameters.AddWithValue("@name", std.name);

This method takes an object as the value and there is no DataType type checking. that could leads to error if SQL Table column is of different type.