通过参数提取结果时出错

Question

我正试图通过下拉选择来提取结果，该下拉选择具有日期范围选项，如今天、每周、每月、每年

protected void ddlFilter_SelectedIndexChanged(object sender, EventArgs e)
    {
        DateTime StartDate;
        DateTime? EndDate;
        if (ddlFilter.SelectedValue == "today")
        {
            //StartDate = Convert.ToInt32(ddlFilter.SelectedValue)
            StartDate = DateTime.Today;
            EndDate = DateTime.Today;
        }
        if (ddlFilter.SelectedValue == "weekly")
        {
            StartDate = DateTime.Today;
            EndDate = DateTime.Now.AddDays(-7).Date;
        }
        if (ddlFilter.SelectedValue == "byweekly")
        {
            StartDate = DateTime.Today;
            EndDate = DateTime.Now.AddDays(-15).Date;
        }
        if (ddlFilter.SelectedValue == "monthly")
        {
            StartDate = DateTime.Today;
            EndDate = DateTime.Now.AddMonths(-1).Date;
        }
        if (ddlFilter.SelectedValue == "yearly")
        {
            StartDate = DateTime.Today;
            EndDate = DateTime.Now.AddYears(-1).Date;
        }
        FillGridFilter(StartDate, EndDate);
    }
private void FillGridFilter(DateTime StartDate, DateTime? EndDate)
    {
        if (EndDate != null)
        {
            hdnid.Value = EndDate.ToString();
        }
        grdCrew.DataSource = null;
        DataTable dtbl = BIZ.ReportsBIZAdmin.ReportsCityFilter(StartDate, EndDate).Tables[0];
        if (dtbl != null && dtbl.Rows.Count > 0)
        {
            grdCrew.DataSource = dtbl;
            grdCrew.DataBind();
            ViewState["griddata"] = dtbl;
        }
        else
        {
            grdCrew.DataSource = null;
            grdCrew.DataBind();
            ViewState["griddata"] = null;
        }
    }

现在它在"FillGridFilter(StartDate, EndDate);"上给出的错误是Use of unassigned local variable 'EndDate'和Use of unassigned local variable 'EndDate'

和

DataTable dtbl = BIZ.ReportsBIZAdmin.ReportsCityFilter(StartDate, EndDate).Tables[0];

说The best overloaded method match for 'BIZ.ReportsBIZAdmin.ReportsCityFilter(System.DateTime, System.DateTime)' has some invalid arguments

存储过程似乎运行良好，它是：

if @end_date = 'today' 
begin
    select jp.id, city.name[City]
    from rs_job_posting jp
    inner join rs_job_posting_location jpl on jpl.id = jp.id
    inner join rs_cor_city city on city.id = jpl.city_fk
    inner join rs_organization_detail od on od.id = jp.id
    where posting_date between '@start_date' and '@end_date'
    order by no_of_posts Desc 
END

Answer 1

因为EndDate是可以为null的，所以在声明它时必须为它赋值（甚至为null）。

DateTime? EndDate = null;

至于第二个错误，您应该使用nullable的属性Value（您应该首先检查它是否有值）来获得DateTime对象：

if (EndDate.HasValue)
    DataTable dtbl = BIZ.ReportsBIZAdmin.ReportsCityFilter(StartDate, EndDate.Value).Tables[0];