Question

我有一个下拉列表。我已使用此代码

将默认值添加到下拉列表框中

<asp:DropDownList ID="DDLCase" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DDLCase_SelectedIndexChanged" AppendDataBoundItems="true" >
<asp:ListItem Value="">Select Member Report ID</asp:ListItem>
</asp:DropDownList>

例如，我有DB值，例如123,1234。

当我运行我的webform并点击123和1234时没有任何反应。但是，当我去点击ListItem值时，他们给了我一些错误

Conversion failed when converting the varchar value 'Select Member Report ID' to data type int.

这是我的网页加载时DDL的后端代码。

 protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {

            SqlConnection con = new SqlConnection("Data Source = localhost; Initial Catalog = project; Integrated Security = SSPI");

            SqlCommand cm = new SqlCommand("Select pr.policereportid from PoliceReport pr, AdminOfficialReport aor, MemberReport mr where pr.memberreportid=mr.memberreportid and mr.caseprogress='settled' and aor.officialreport IS NULL", con);
            con.Open();
            SqlDataReader dr;
            dr = cm.ExecuteReader();
            while (dr.Read())
            {
                DDLCase.Items.Add(dr["policereportid"].ToString());
            }
            DDLCase.Items.Insert(0, new ListItem("Select Member Report ID", "-1"));

            dr.Close();
            con.Close();
        }
    }

这是我的错误发生的地方。它发生在dr = cm.ExecuteReader（）;

周围的区域

protected void DDLCase_SelectedIndexChanged(object sender, EventArgs e)
    {

        SqlConnection con = new SqlConnection("Data Source = localhost; Initial Catalog = project; Integrated Security = SSPI");
        con.Open();
        SqlCommand cm = new SqlCommand("Select lro.fullname, lro.contact, mr.typeofcrime, mr.location,mr.crdatetime, pr.policeid, pr.prdatetime, pr.policereport, pr.image1, mr.citizenreport from MemberReport mr, PoliceReport pr, LoginRegisterOthers lro where pr.policereportid = '" + DDLCase.SelectedItem.Text + "' and mr.memberreportid=pr.memberreportid and lro.username=mr.username and mr.caseprogress='settled'", con);
        SqlDataReader dr;
        dr = cm.ExecuteReader();
        if (dr.Read())
        {
            lblFullName.Text = dr["fullname"].ToString();
            lblContact.Text = dr["contact"].ToString();
            lblTOC.Text = dr["typeofcrime"].ToString();
            lblLocation.Text = dr["location"].ToString();
            lblCRDT.Text = dr["crdatetime"].ToString();
            lblPicture.Text = dr["image1"].ToString();
            lblAssign.Text = dr["policeid"].ToString();
            lblPRDT.Text = dr["prdatetime"].ToString();
            lblCR.Text = dr["citizenreport"].ToString();
            lblPR.Text = dr["policereport"].ToString();
        }

        con.Close();

    }

我如何解决这个问题？

Answer 1

因为它期望一个int类型的值，并且在默认情况下没有设置值，因此它正在拾取选项字段中的文本，即Select Member Report ID

将其更改为：

<asp:ListItem Value="-1">Select Member Report ID</asp:ListItem>

并在/ javascript

后面的代码中正确处理负值

使用SelectedValue而不是Text！

SqlCommand cm = new SqlCommand("Select lro.fullname, lro.contact, mr.typeofcrime, mr.location,mr.crdatetime, 
pr.policeid, pr.prdatetime, pr.policereport, pr.image1, mr.citizenreport from MemberReport mr, PoliceReport pr, 
LoginRegisterOthers lro where pr.policereportid = '" + DDLCase.SelectedValue + "' and 
mr.memberreportid=pr.memberreportid and lro.username=mr.username and mr.caseprogress='settled'", con);

Answer 2

从标记中删除<asp:ListItem Value="">Select Member Report ID</asp:ListItem>这行代码。绑定你的DDL后，只需写下这一行

DDLID.items.insert(0,listboxitem("Select Member Report ID","-1"));

现在让您的代码看起来像

int index = 1; while（dr.Read（）） { if（index == 1） { DDLCase.Items.Insert（0，new ListItem（“Select Member Report ID”，“ - 1”））;

} 其他 { DDLCase.Items.Add（new ListItem（dr [“dataId”]。toString（），index））; } 索引++;

}

在下拉列表中使用confirmbuttonextender时重复值

2 个答案: