如何使用ADO.Net C＃将null插入到sql数据库中

Question

i have a DropDownList that display a collection of subset based on SetID from another ddl and some times it is null. how i can insert null value into database ? i tried with this code but not work:

CmdUpdate.Parameters.Add("@SubsetID",SqlDbType.Int);
if (ddlSubset.Items.Count!=0)
{
  CmdUpdate.Parameters["@SubsetID"].Value=ddlSubset.SelectedValue;
}
esle
{
  CmdUpdate.Parameters["@SubsetID"].Value=null;
}

Answer 1

使用System.DBNull类：

CmdUpdate.Parameters["@SubsetID"].Value = DBNull.Value;

Answer 2

使用DBNull：

CmdUpdate.Parameters["@SubsetID"].Value = DBNull.Value;