Question

这是我的表：

roomtype, number of rooms
Ac        10

我想从表中检索值并将房间减去1并更新上表。如何使用C＃在ASP.NET中编写检索代码？

这是更新后的代码。它显示dt.Rows[0]["no_of_rooms"] > 1中的错误，表示无法将对象类型与int进行比较。但是在将此no_of_rooms解析为int时，错误仍然相同。

public partial class Book_Room : System.Web.UI.Page
{
    protected void Button1_Click(object sender, EventArgs e)
    {
        string type = DropDownList1.SelectedItem.ToString();
        string name = TextBox2.Text;
        string nop = DropDownList2.SelectedItem.ToString();
        int num = int.Parse(nop);
        string connectionString = WebConfigurationManager.ConnectionStrings["HMSConnectionString"].ConnectionString;
        SqlConnection connection = new SqlConnection(connectionString);

        string qry3 = "select * from availiability where RoomType=@type";
        SqlCommand cmd3 = new SqlCommand(qry3, connection);
        cmd3.Parameters.AddWithValue("@type", type);
        cmd3.ExecuteReader();
        SqlDataAdapter ad = new SqlDataAdapter(cmd3);
        DataTable dt = new DataTable();
        if (dt.Rows.Count > 0)
        {    
            if (dt.Rows[0]["no_of_rooms"] > 1)
            {
                string qry = "insert into RoomType values('" + type + "','" + name + "','" + num + "') ";
                SqlCommand cmd = new SqlCommand(qry, connection);
                connection.Open();
                int g = cmd.ExecuteNonQuery();
                if (g != 0)
                    Label5.Text = "Reserved for" + name;
                connection.Close();

                string qry2 = "update availiability set RoomType=@type ,availiable_rooms=@av";
                SqlCommand cmd2 = new SqlCommand(qry2, connection);
                cmd2.Parameters.AddWithValue("@type", type);
                cmd2.Parameters.AddWithValue("@av", dt.Rows[0]["no_of_rooms"] - 1);
                connection.Open();
                cmd2.ExecuteNonQuery();
                connection.Close();
            }
        }

        else
        {
            label5.Text = "No Rooms Availiable in " + type;
        }
    }
}

Answer 1

将其更改为此(int)dt.Rows[0]["no_of_rooms"] > 1。

Answer 2

或者你可以尝试

dt.Rows[0].Field<int>("no_of_rooms")>1

Answer 3

您没有使用查询返回的任何其他值，因此创建SqlDataAdapater并填充Table有点多。

我建议改用ExecuteScalar。这将从数据库中返回单个值。

string qry3 = "select * from availiability where RoomType=@type";
SqlCommand cmd3 = new SqlCommand(qry3, connection);
cmd3.Parameters.AddWithValue("@type", type);
object objCount = command.ExecuteScalar();
int count = objCount == null ? 0 : (int)objCount;
if (count > 0)
{
    // Do other things
}

错误：无法将对象类型与int进行比较

3 个答案: