c# - C#问题，向现有数据表添加新行

Question

我试图在onClick上添加新行。但是，它取代了我现有的添加到新行的行瞬间。

以下是代码：

Main.cs

protected void Button1_Click(object sender, EventArgs e)
{
    DateTime selectedDate = CalendarMain.SelectedDate;
    string SportType = ddlSportType.SelectedItem.ToString();
    string distance = ddlDistance.SelectedItem.ToString();

    plan wp = new plan();
    wp.Time_Start = selectedDate;
    wp.Duration = distance;
    wp.Activity = SportType;

    DataTable dt = wp.addPlanDetailDataRow();

    gvActivityList.DataSource = dt;
    gvActivityList.DataBind();
}

plan.cs

public DataTable addPlanDetailDataRow()
{
    DataTable dt = new DataTable();

    dt.Columns.Add("Activity");
    dt.Columns.Add("Duration");
    dt.Columns.Add("status");
    dt.Columns.Add("Time_Start");
    dt.Columns.Add("Plan_ID");

    DataRow newRow = dt.NewRow();

    dt.Rows.Add(newRow);

    return dt;
}

我不确定我错过了什么。请指导我有关我的错误。非常感谢

Answer 1

使用ViewState记住以前的值：

编辑：-

  protected void Button1_Click(object sender, EventArgs e)
{
    DateTime selectedDate = CalendarMain.SelectedDate;
    string SportType = ddlSportType.SelectedItem.ToString();
    string distance = ddlDistance.SelectedItem.ToString();
    plan wp = new plan();
    wp.Time_Start = selectedDate;
    wp.Duration = distance;
    wp.Activity = SportType;

    DataTable dt = new DataTable();

    dt.Columns.Add("Activity");
    dt.Columns.Add("Duration");
    dt.Columns.Add("status");
    dt.Columns.Add("Time_Start");
    dt.Columns.Add("Plan_ID");


    DataTable dt1 = wp.addPlanDetailDataRow(dt);

    gvActivityList.DataSource = dt;
    gvActivityList.DataBind();
}
public DataTable addPlanDetailDataRow(DataTable dt)
{

     if (ViewState["Datatable"] != null)
    {
        dt = (DataTable)ViewState["Datatable"];
    }
    ViewState["Datatable"] = dt;
    DataRow dr = dt.NewRow();
    dr["Activity"]="value1";
    dr["Duration"]="value2";
    dr["status"]="value3";
    dr["Time_Start"]="value4";
    dr["Plan_ID"]="value5";

    dt.Rows.Add(dr);

    return dt;
}