Question

我有一个由以下查询填充的下拉列表。该列表从不是静态的，因此列表中的项目总数将不同。

<asp:SqlDataSource ID="SqlDataSource" runat="server" ConnectionString="<%$ ConnectionStrings:testConnectionString %> " SelectCommand="SELECT * FROM TABLE WHERE STATUS = 'done' "></asp:SqlDataSource>

我知道我试图在我的下拉列表中访问一个不存在的索引。是否存在以避免选择不存在的索引？

    private DataTable test()
{
    DataTable dt = new DataTable();
    SqlDataAdapter Adpt;

    using (SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["testConnectionString"].ConnectionString))
    {
        SqlCommand cmd = new SqlCommand("SELECT * FROM TABLE WHERE id=@id", con);
        cmd.Parameters.AddWithValue("@id", ddlsubnum.Items[0].Text);
        Adpt = new SqlDataAdapter(cmd);
        new SqlDataAdapter(cmd).Fill(dt);
    }
    Chart1.Series["Series1"].YValueMembers = "recs";
    Chart1.Series["Series1"].XValueMember = "date";
    Chart1.Series["Series1"].XValueType = ChartValueType.DateTime;
    Chart1.Series["Series1"].YValueType = ChartValueType.Int32;

    return dt;
}

private DataTable test2()
{
    DataTable dt2 = new DataTable();
    SqlDataAdapter Adpt;

    using (SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["testConnectionString"].ConnectionString))
    {
        SqlCommand cmd = new SqlCommand("SELECT * FROM TABLE WHERE id=@id", con);
        cmd.Parameters.AddWithValue("@id", ddlsubnum.Items[1].Text);
        Adpt = new SqlDataAdapter(cmd);
        new SqlDataAdapter(cmd).Fill(dt2);
    }
    Chart2.Series["Series1"].YValueMembers = "recs";
    Chart2.Series["Series1"].XValueMember = "date";
    Chart2.Series["Series1"].XValueType = ChartValueType.DateTime;
    Chart2.Series["Series1"].YValueType = ChartValueType.Int32;

    return dt2;
}

我在按钮点击事件上运行此功能。

    protected void Button1_Click(object sender, EventArgs e)
{
    {
        DataTable dt = this.test();
        Chart1.DataSource = dt;
        Chart1.DataBind();
    }

    {
        DataTable dt2 = this.test2();
        Chart2.DataSource = dt2;
        Chart2.DataBind();
    }
}

Answer 1

好像我们在这里遗漏了一些东西......所以我现在可以建议的是......

string forQRY = ddlsubnum.Items.Count > 0 ? ddlsubnum.Items[0].Text : "";//if the list has items, populate index 0 from list, otherwise empty string""
cmd.Parameters.AddWithValue("@id", forQRY);

我不明白你期望能够选择一些不存在的东西......

指数超出范围。必须是非负数且小于集合的大小。参数名称：index dropdownlist

1 个答案: