Question

我使用asp图表控件在图表上显示数据库中的一些值。但是，我面临以下错误，我已通过单行注释指定。

  protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            string query = "select distinct name from tblDars";
            DataTable dt = GetData(query);
            ddlSubject.DataSource = dt;
            ddlSubject.DataTextField = "tblDars";
            ddlSubject.DataValueField = "tblDars";
            //ddlSubject.DataBind();
            ddlSubject.Items.Insert(0, new ListItem("Select", ""));
        }
    }

控件的标记如下：

<asp:DropDownList ID="ddlSubject" runat="server"
onselectedindexchanged="ddlSubjectChanged" AutoPostBack = "true">
</asp:DropDownList><hr />
<asp:Chart ID="Chart1" runat="server" Height="300px" Width="400px" Visible = "false">
    <Titles>
        <asp:Title ShadowOffset="3" Name="Items" />
    </Titles>
    <Legends>
        <asp:Legend Alignment="Center" Docking="Top" IsTextAutoFit="False" Name="Default" LegendStyle="Row" />
    </Legends>
    <Series>
        <asp:Series Name="درس" />
    </Series>
    <ChartAreas>
        <asp:ChartArea Name="ChartArea1" BorderWidth="0" />
    </ChartAreas>
</asp:Chart>

我在课堂上还有两个其他功能;
一个用于事件处理，另一个用于执行数据库作业;它们如下所示：

 protected void ddlSubjectChanged(object sender, EventArgs e)
    {
        Chart1.Visible = ddlSubject.SelectedValue != "";
        //string query = string.Format("select shipcity, count(orderid) from orders where shipcountry = '{0}' group by shipcity", ddlSubject.SelectedValue);
        string query = string.Format("select Name, count (id) from tblDars where Name='{0}' group by Name", ddlSubject.SelectedValue);
        DataTable dt = GetData(query);
        string[] x = new string[dt.Rows.Count];
        int[] y = new int[dt.Rows.Count];
        for (int i = 0; i < dt.Rows.Count; i++)
        {
            x[i] = dt.Rows[i][0].ToString();
            y[i] = Convert.ToInt32(dt.Rows[i][1]);
        }
        Chart1.Series[0].Points.DataBindXY(x, y);
        Chart1.Series[0].ChartType = SeriesChartType.Bar;
        Chart1.ChartAreas["ChartArea1"].Area3DStyle.Enable3D = false;
        Chart1.Legends[0].Enabled = true;
    }

        private static DataTable GetData(string query)
    {
        DataTable dt = new DataTable();
        SqlCommand cmd = new SqlCommand(query);
        String constr = ConfigurationManager.ConnectionStrings["SchoolConnectionString"].ConnectionString;
        SqlConnection con = new SqlConnection(constr);
        SqlDataAdapter sda = new SqlDataAdapter();
        cmd.CommandType = CommandType.Text;
        cmd.Connection = con;
        sda.SelectCommand = cmd;
        sda.Fill(dt);
        return dt;
    }

一切似乎都好我不知道错误来自何处。

Answer 1

你回来＆＃34;名字＆＃34; db中的列，但您要设置无效的列名

在DataTextField和DataValueField中指定有效列。

ddlSubject.DataTextField = "name";
 ddlSubject.DataValueField = "name";

Chart控件的数据绑定失败

1 个答案: