C# 无法使用asp.net中的多个字段对DDL进行排序

我正在尝试对动态创建的DDL进行排序。此DDL包含位置1、位置2和位置3字段的组合

用于创建DDL的代码如下所示：

        ddlLocation.Items.Clear();
        dtLocation = dataSource.GetFilteredRiskInfo("location");
        ddlLocation.Items.Insert(0, new ListItem("All", "-1"));
        foreach (DataRow row in dtLocation.Rows)
        {
            if (this.ddlLocation.Items.FindByText(row["Location1"].ToString()) == null)
                this.ddlLocation.Items.Add(new ListItem(row["Location1"].ToString()));
            if (this.ddlLocation.Items.FindByText(row["Location2"].ToString()) == null)
                this.ddlLocation.Items.Add(new ListItem(row["Location2"].ToString()));
            if (this.ddlLocation.Items.FindByText(row["Location3"].ToString()) == null)
                this.ddlLocation.Items.Add(new ListItem(row["Location3"].ToString()));
        }

            ddlLocation.Items.Clear();
        // new table to combine the 3 columns of dtLocation into a one column datatable
        DataTable sortedDt = new DataTable();
        dtLocation = dataSource.GetFilteredRiskInfo("location");
        sortedDt.Columns.Add("Location");

        // combining columns
        foreach (DataRow row in dtLocation.Rows)
        {
            sortedDt.Rows.Add(row["Location1"]);
            sortedDt.Rows.Add(row["Location2"]);
            sortedDt.Rows.Add(row["Location3"]);
        }

        // now sort these now that they're all in the same column
        sortedDt.DefaultView.Sort = "Location";
        sortedDt = sortedDt.DefaultView.ToTable(); // should be the new sorted table

        // now your original code, but modified to populate the ddl with the new sorted data


        ddlLocation.Items.Insert(0, new ListItem("All", "-1"));
        foreach (DataRow row in sortedDt.Rows)
        {
            this.ddlLocation.Items.Add(new ListItem(row["Location"].ToString()));
        }

           //Location
        ddlLocation.Items.Clear();
        // new table to combine the 3 columns of dtLocation into a one column datatable
        DataTable sortedDt = new DataTable();
        sortedDt.Columns.Add("Location");
        dtLocation = dataSource.GetFilteredRiskInfo("location");

        // combining columns
        foreach (DataRow row in dtLocation.Rows)
        {
            sortedDt.Rows.Add(row["Location1"]);
            sortedDt.Rows.Add(row["Location2"]);
            sortedDt.Rows.Add(row["Location3"]);
        }

        // now make them distinct & sort them now that they're all in the same column
        sortedDt = sortedDt.DefaultView.ToTable(/*distinct*/ true);
        sortedDt.DefaultView.Sort = "Location";
        sortedDt = sortedDt = sortedDt.DefaultView.ToTable();

        // now your original code, but modified to populate the ddl with the new sorted data
        ddlLocation.Items.Insert(0, new ListItem("All", "-1"));
        foreach (DataRow row in sortedDt.Rows)
        {
            this.ddlLocation.Items.Add(new ListItem(row["Location"].ToString()));
        }

以下代码适用于位置1（我认为）

我一直在研究如何添加多个字段，即：location2和location3，它不起作用。代码本身显示Location1和Location2的错误（“名称“Location1”在当前上下文中不存在”）

所有的帮助都将是非常感激的

位置列表需要如下所示。假设这些位置具有以下数据

地点1： 悉尼，卧龙岗珀斯

地点2： 阿德莱德，北领地

地点3： 布里斯班、堪培拉、霍巴特

我需要组合列表如下所示： 阿德莱德 布里斯班 堪培拉 霍巴特 北领地 珀斯 悉尼 卧龙岗

我的代码现在如下所示：

        ddlLocation.Items.Clear();
        dtLocation = dataSource.GetFilteredRiskInfo("location");
        ddlLocation.Items.Insert(0, new ListItem("All", "-1"));
        foreach (DataRow row in dtLocation.Rows)
        {
            if (this.ddlLocation.Items.FindByText(row["Location1"].ToString()) == null)
                this.ddlLocation.Items.Add(new ListItem(row["Location1"].ToString()));
            if (this.ddlLocation.Items.FindByText(row["Location2"].ToString()) == null)
                this.ddlLocation.Items.Add(new ListItem(row["Location2"].ToString()));
            if (this.ddlLocation.Items.FindByText(row["Location3"].ToString()) == null)
                this.ddlLocation.Items.Add(new ListItem(row["Location3"].ToString()));
        }

            ddlLocation.Items.Clear();
        // new table to combine the 3 columns of dtLocation into a one column datatable
        DataTable sortedDt = new DataTable();
        dtLocation = dataSource.GetFilteredRiskInfo("location");
        sortedDt.Columns.Add("Location");

        // combining columns
        foreach (DataRow row in dtLocation.Rows)
        {
            sortedDt.Rows.Add(row["Location1"]);
            sortedDt.Rows.Add(row["Location2"]);
            sortedDt.Rows.Add(row["Location3"]);
        }

        // now sort these now that they're all in the same column
        sortedDt.DefaultView.Sort = "Location";
        sortedDt = sortedDt.DefaultView.ToTable(); // should be the new sorted table

        // now your original code, but modified to populate the ddl with the new sorted data


        ddlLocation.Items.Insert(0, new ListItem("All", "-1"));
        foreach (DataRow row in sortedDt.Rows)
        {
            this.ddlLocation.Items.Add(new ListItem(row["Location"].ToString()));
        }

           //Location
        ddlLocation.Items.Clear();
        // new table to combine the 3 columns of dtLocation into a one column datatable
        DataTable sortedDt = new DataTable();
        sortedDt.Columns.Add("Location");
        dtLocation = dataSource.GetFilteredRiskInfo("location");

        // combining columns
        foreach (DataRow row in dtLocation.Rows)
        {
            sortedDt.Rows.Add(row["Location1"]);
            sortedDt.Rows.Add(row["Location2"]);
            sortedDt.Rows.Add(row["Location3"]);
        }

        // now make them distinct & sort them now that they're all in the same column
        sortedDt = sortedDt.DefaultView.ToTable(/*distinct*/ true);
        sortedDt.DefaultView.Sort = "Location";
        sortedDt = sortedDt = sortedDt.DefaultView.ToTable();

        // now your original code, but modified to populate the ddl with the new sorted data
        ddlLocation.Items.Insert(0, new ListItem("All", "-1"));
        foreach (DataRow row in sortedDt.Rows)
        {
            this.ddlLocation.Items.Add(new ListItem(row["Location"].ToString()));
        }

---

现在列表按字母顺序排列，但有重复条目。我需要能够删除重复项/使条目不同。

不仅应该按照FrankO的建议在GetFilteredRiskInfo中对其进行预排序，而且听起来好像必须将3个位置列合并为一个。如果您可以在GetFilteredRiskInfo中这样做，它可能会更干净，如果不能，您可以尝试将列和代码排序与以下内容结合起来：

    // new table to combine the 3 columns of dtLocation into a one column datatable
    DataTable sortedDt = new DataTable();
    sortedDt.Columns.Add("Location");

    // combining columns
    foreach (DataRow row in dtLocation.Rows)
    {
        sortedDt.Rows.Add(row["Location1"]);
        sortedDt.Rows.Add(row["Location2"]);
        sortedDt.Rows.Add(row["Location3"]);
    }

    // now sort these now that they're all in the same column
    sortedDt.DefaultView.Sort = "Location";
    sortedDt = sortedDt.DefaultView.ToTable(); // should be the new sorted table

    // now your original code, but modified to populate the ddl with the new sorted data
    ddlLocation.Items.Clear();
    dtLocation = dataSource.GetFilteredRiskInfo("location");
    ddlLocation.Items.Insert(0, new ListItem("All", "-1"));
    foreach (DataRow row in sortedDt.Rows)
    {
            this.ddlLocation.Items.Add(new ListItem(row["Location"].ToString()));
    }

感谢FronkO（我现在在所有下拉列表中都有排序列表）和madamission（在位置排序方面的额外帮助）。在你们两个和一些来自互联网的帮助下，我现在让它工作了。工作守则如下：

        ddlLocation.Items.Clear();
        dtLocation = dataSource.GetFilteredRiskInfo("location");
        ddlLocation.Items.Insert(0, new ListItem("All", "-1"));
        foreach (DataRow row in dtLocation.Rows)
        {
            if (this.ddlLocation.Items.FindByText(row["Location1"].ToString()) == null)
                this.ddlLocation.Items.Add(new ListItem(row["Location1"].ToString()));
            if (this.ddlLocation.Items.FindByText(row["Location2"].ToString()) == null)
                this.ddlLocation.Items.Add(new ListItem(row["Location2"].ToString()));
            if (this.ddlLocation.Items.FindByText(row["Location3"].ToString()) == null)
                this.ddlLocation.Items.Add(new ListItem(row["Location3"].ToString()));
        }

            ddlLocation.Items.Clear();
        // new table to combine the 3 columns of dtLocation into a one column datatable
        DataTable sortedDt = new DataTable();
        dtLocation = dataSource.GetFilteredRiskInfo("location");
        sortedDt.Columns.Add("Location");

        // combining columns
        foreach (DataRow row in dtLocation.Rows)
        {
            sortedDt.Rows.Add(row["Location1"]);
            sortedDt.Rows.Add(row["Location2"]);
            sortedDt.Rows.Add(row["Location3"]);
        }

        // now sort these now that they're all in the same column
        sortedDt.DefaultView.Sort = "Location";
        sortedDt = sortedDt.DefaultView.ToTable(); // should be the new sorted table

        // now your original code, but modified to populate the ddl with the new sorted data


        ddlLocation.Items.Insert(0, new ListItem("All", "-1"));
        foreach (DataRow row in sortedDt.Rows)
        {
            this.ddlLocation.Items.Add(new ListItem(row["Location"].ToString()));
        }

           //Location
        ddlLocation.Items.Clear();
        // new table to combine the 3 columns of dtLocation into a one column datatable
        DataTable sortedDt = new DataTable();
        sortedDt.Columns.Add("Location");
        dtLocation = dataSource.GetFilteredRiskInfo("location");

        // combining columns
        foreach (DataRow row in dtLocation.Rows)
        {
            sortedDt.Rows.Add(row["Location1"]);
            sortedDt.Rows.Add(row["Location2"]);
            sortedDt.Rows.Add(row["Location3"]);
        }

        // now make them distinct & sort them now that they're all in the same column
        sortedDt = sortedDt.DefaultView.ToTable(/*distinct*/ true);
        sortedDt.DefaultView.Sort = "Location";
        sortedDt = sortedDt = sortedDt.DefaultView.ToTable();

        // now your original code, but modified to populate the ddl with the new sorted data
        ddlLocation.Items.Insert(0, new ListItem("All", "-1"));
        foreach (DataRow row in sortedDt.Rows)
        {
            this.ddlLocation.Items.Add(new ListItem(row["Location"].ToString()));
        }

---

为什么不合并所有三个位置的字符串，然后将该字符串添加到ddl中？您希望列表项显示

Location1+Location2

？为什么在调用GetFilteredRiskInfo（）时没有排序？然后，当您在数据行中循环时，它将被预排序。