数据库数据查询

Question

我查询了数据库中的一个表，想实现如果表中有数据则执行一些操作，没数据则不执行，代码如下
SqlConnection cona = new SqlConnection("server=.;database=superet;Trusted_Connection=True");
            SqlCommand cmda = new SqlCommand();
            cona.Open();
            cmda.Connection = cona;
            string stra = "select *  from sell where 销售日期 between '" + this.dateTimePicker1.Text.ToString() + "' and '" + this.dateTimePicker2.Text.ToString() + "'";
            SqlDataAdapter adaa = new SqlDataAdapter(stra, cona);                      
            DataSet dsa = new DataSet();
            adaa.Fill(dsa);            
            cona.Close();
            if (dsa != null)
            {
                comboBox1.Items.Clear();
                SqlConnection cona1 = new SqlConnection("server=.;database=superet;Trusted_Connection=True");
                SqlCommand cmda1 = new SqlCommand();
                cona1.Open();
                cmda1.Connection = cona1;
                string stra1 = "select Sum(货物数量)  from sell where 销售日期 between '" + this.dateTimePicker1.Text.ToString() + "' and '" + this.dateTimePicker2.Text.ToString() + "'";
                SqlDataAdapter adaa1 = new SqlDataAdapter(stra1, cona1);
                DataTable dta1 = new DataTable();                
                adaa1.Fill(dta1);
                cona1.Close();
                this.button1.Enabled = true;
                SumNum = Convert.ToInt32(dta1.Rows[0][0].ToString());                SqlConnection cona11 = new SqlConnection("server=.;database=superet;Trusted_Connection=True");
                SqlCommand cmda11 = new SqlCommand();
                cona11.Open();
                cmda11.Connection = cona11;
                string stra11 = "select distinct (cast(货物名称 as varchar(8000))) from sell where 销售日期 between '" + this.dateTimePicker1.Text.ToString() + "' and '" + this.dateTimePicker2.Text.ToString() + "'";
                SqlDataAdapter adaa11 = new SqlDataAdapter(stra11, cona11);
                DataTable dta11=new DataTable();
               
                adaa11.Fill(dta11);
                cona11.Close();
                for (int i = 0; i < dta11.Rows.Count; i++)
                {
                    comboBox1.Items.Add(dta11.Rows[i][0]);
                }            
            } 
但是没有数据时还是会执行if里的语句，怎么让他没数据的时候跳过去？                     

Answer 1

将“if (dsa != null)”替换为“ if(DataSet.Tables[?].Rows.Count==0)”试试

Answer 2

正解
我做了个测试
  DataSet ds = new DataSet();
                if (ds == null)
                {
                    Response.Write("Yes it's Null");
                }
                else
                {
                    Response.Write("No it's not Null");
                }
返回为 No it's not Null 说明当你 DataSet dsa = new DataSet();后dsa 就不可以是NULL了
用上面仁兄的办法吧

Answer 3

 if (dsa != null&& dsa .Tables[?].Rows.Count==0)

Answer 4

應該先判斷Dataset是否為空的,用Dataset.Table[0].Rows.Count來判斷！

Answer 5

if (dsa != null&& dsa .Tables[?].Rows.Count!=0)