如何从下拉列表中选择一个值并将值传递给 Gridview？答案

【问题标题】：How to select a value from Dropdownlist and pass value to Gridview?如何从下拉列表中选择一个值并将值传递给 Gridview？
【发布时间】：2018-04-14 04:38:55
【问题描述】：

我的 SQL 语句无法将下拉列表选择中的值传递到我的网格视图。我用特定的日期测试了我的 SQL 语句 Serve Management Studio，它可以工作，但它不适用于我的下拉列表中的选择值。我如何将值传递给 Gridview？感谢您的帮助，我是 asp.net 世界的新学生。

网络应用程序的图像：我的数据库的图像：

public void RefreshDay()
        {
            SqlConnection conn = new SqlConnection(@"data source =.\sqlexpress; integrated security = true; database = DBdentist");
            SqlDataAdapter da = null;
            DataSet ds = null;
            DataTable dt = null;
            string sqlsel = "SELECT Distinct patient.patientID, day from patient, patientreservation where patient.patientID = patientreservation.patientID";


        try
        {

            da = new SqlDataAdapter();  
            da.SelectCommand = new SqlCommand(sqlsel, conn);  
            ds = new DataSet();
            da.Fill(ds, "myDay");   
            dt = ds.Tables["myDay"];   


            DropDownListDay.DataSource = dt;
            DropDownListDay.DataTextField = "day";
            DropDownListDay.DataValueField = "patientID";
            DropDownListDay.DataBind();
            DropDownListDay.Items.Insert(0, "Select Day"); 
        }
        catch (Exception ex)
        {
            LabelDay.Text = ex.Message; 
        }
        finally
        {
            conn.Close(); 
        }

    }



    protected void DropDownListDay_SelectedIndexChanged(object sender, EventArgs e)
    {
        if (DropDownListDay.SelectedIndex != 0)
        {
            SqlConnection conn = new SqlConnection(@"data source =.\sqlexpress; integrated security = true; database = DbDentist");
            SqlDataAdapter da = null;
            DataSet ds = null;
            DataTable dt = null;
            string sqlsel = "SELECT patientreservation.patientID, patient.firstname, patient.lastname, patientreservation.day, patientreservation.hour, treatment.treatment FROM((patientreservation INNER JOIN patient ON patientreservation.patientID = patient.patientID) INNER JOIN treatment ON patientreservation.treatmentID = treatment.treatmentID) WHERE patientreservation.day = " + DropDownListDay.SelectedValue + "";

            try
            {

                da = new SqlDataAdapter();  
                da.SelectCommand = new SqlCommand(sqlsel, conn); 
                ds = new DataSet();
                da.Fill(ds, "myDay");  
                dt = ds.Tables["myDay"];
                GridViewDay.DataSource = dt; 
                GridViewDay.DataBind();

            }
            catch (Exception ex)
            {
                LabelDay.Text = ex.Message; 
            }
            finally
            {
                conn.Close(); 
            }

        }

        else
        {
            LabelDay.Text = "You choose None:";
        }
    }
}

}

【问题讨论】：

DropDownListDay.SelectedValue 应该是数值吗？还是像“星期一”或类似的东西
数据类型是日期...'2017-07-05'
SELECT patientreservation.patientID，patient.firstname，patient.lastname，patientreservation.day，patientreservation.hour，treatment.treatment FROM ((patientreservation INNER JOIN patient ON patientreservation.patientID=patient.patientID) INNER JOIN治疗 ON patientreservation.treatmentID =treatment.treatmentID) WHERE patientreservation.day = '2017-07-05' 这在我测试时工作正常，但是当我添加所选值时我开始遇到问题
日期周围的那些单引号不在您的代码中。
我已经尝试了几次单引号但没有运气......

标签： c# sql asp.net gridview

【解决方案1】：

你可以简单地使用这个：

WHERE patientreservation.day = '" + DropDownListDay.Text.ToString() + "'";

【讨论】：

【解决方案2】：

感谢您的帮助。我什么都试过了

DropDownListDay.DataTextField = "day"; DropDownListDay.DataValueField = "day"

帮助。我的gridview也有一些问题。我加起来删除它并制作一个新的，不知何故有帮助。

【讨论】：

【解决方案3】：

你的下拉菜单的配置是

DropDownListDay.DataTextField = "day";
DropDownListDay.DataValueField = "patientID";

但如果您想使用当前选定的值进行过滤，则需要将 day 作为值

DropDownListDay.DataTextField = "day";
DropDownListDay.DataValueField = "day";

SELECT patientreservation.patientID, patient.firstname, patient.lastname, patientreservation.day, patientreservation.hour, treatment.treatment FROM((patientreservation INNER JOIN patient ON patientreservation.patientID = patient.patientID) INNER JOIN treatment ON patientreservation.treatmentID = treatment.treatmentID) WHERE **patientreservation.day** = " + DropDownListDay.**SelectedValue** + "";

或者你可以试试WHERE **patientreservation.day** = " + DropDownListDay.**SelectedText** + "";

【讨论】：

仍然无法通过这些更改查看网格视图。对所选文本非常不满意。 DropDownListDay.DataTextField = "天"; DropDownListDay.DataValueField = "天";很有道理，但仍然不确定为什么它不会显示
解决日期时间数据类型问题的方法类似于 $"WHERE DATEDIFF(dd, patientreservation.day, {DropDownListDay.SelectedValue}) =0";如果不起作用，请尝试添加简单的引号

【解决方案4】：

下拉列表未触发事件。尝试将此 AutoPostBack="true" 放在您的 asp 下拉列表标签中。

【讨论】：