Sorting a DropDownList? - C#, ASP.NET

问题:

I'm curious as to the best route (more looking towards simplicity, not speed or efficiency) to sort a DropDownList in C#/ASP.NET - I've looked at a few recommendations but they aren't clicking well with me.

Edit: Folks, I do not have control over how the data comes into the DropDownList - I cannot modify the SQL.

回答1:

If you get a DataTable with the data, you can create a DataView off of this and then bind the drop down list to that. Your code would look something like...

DataView dvOptions = new DataView(DataTableWithOptions);
dvOptions.Sort = "Description";

ddlOptions.DataSource = dvOptions;
ddlOptions.DataTextField = "Description";
ddlOptions.DataValueField = "Id";
ddlOptions.DataBind();

Your text field and value field options are mapped to the appropriate columnns in the data table you are receiving.

回答2:

A C# solution for .NET 3.5 (needs System.Linq and System.Web.UI):

    public static void ReorderAlphabetized(this DropDownList ddl)
    {
        List<ListItem> listCopy = new List<ListItem>();
        foreach (ListItem item in ddl.Items)
            listCopy.Add(item);
        ddl.Items.Clear();
        foreach (ListItem item in listCopy.OrderBy(item => item.Text))
            ddl.Items.Add(item);
    }

Call it after you've bound your dropdownlist, e.g. OnPreRender:

    protected override void OnPreRender(EventArgs e)
    {
        base.OnPreRender(e);
        ddlMyDropDown.ReorderAlphabetized();
    }

Stick it in your utility library for easy re-use.

回答3:

Assuming you are running the latest version of the .Net Framework this will work:

List<string> items = GetItemsFromSomewhere();
items.Sort((x, y) => string.Compare(x, y));
DropDownListId.DataSource = items;
DropDownListId.DataBind();

回答4:

DropDownList takes any IEnumerable as a DataSource.

Just sort it using LINQ.

回答5:

I usually load a DropDownList with values from a database table, so the easiest way is to sort your results as desired with the ORDER BY clause of your SELECT statement, and then just iterate through the results and dump them into the DropDownList.

回答6:

Take a look at the this article from CodeProject, which rearranges the content of a dropdownlist. If you are databinding, you will need to run the sorter after the data is bound to the list.

回答7:

It is recommended to sort the data before databinding it to the DropDownList but in case you can not, this is how you would sort the items in the DropDownList.

First you need a comparison class

Public Class ListItemComparer
    Implements IComparer(Of ListItem)

    Public Function Compare(ByVal x As ListItem, ByVal y As ListItem) As Integer _
        Implements IComparer(Of ListItem).Compare

        Dim c As New CaseInsensitiveComparer
        Return c.Compare(x.Text, y.Text)
    End Function
End Class

Then you need a method that will use this Comparer to sort the DropDownList

Public Shared Sub SortDropDown(ByVal cbo As DropDownList)
    Dim lstListItems As New List(Of ListItem)
    For Each li As ListItem In cbo.Items
        lstListItems.Add(li)
    Next
    lstListItems.Sort(New ListItemComparer)
    cbo.Items.Clear()
    cbo.Items.AddRange(lstListItems.ToArray)
End Sub

Finally, call this function with your DropDownList (after it's been databound)

SortDropDown(cboMyDropDown)

P.S. Sorry but my choice of language is VB. You can use http://converter.telerik.com/ to convert the code from VB to C#

回答8:

Another option is to put the ListItems into an array and sort.

        int i = 0;
        string[] array = new string[items.Count];

        foreach (ListItem li in dropdownlist.items)
        {
            array[i] = li.ToString();
            i++;

        }

        Array.Sort(array);

        dropdownlist.DataSource = array;
        dropdownlist.DataBind();

回答9:

I agree with sorting using ORDER BY when populating with a database query, if all you want is to sort the displayed results alphabetically. Let the database engine do the work of sorting.

However, sometimes you want some other sort order besides alphabetical. For example, you might want a logical sequence like: New, Open, In Progress, Completed, Approved, Closed. In that case, you could add a column to the database table to explicitly set the sort order. Name it something like SortOrder or DisplaySortOrder. Then, in your SQL, you'd ORDER BY the sort order field (without retrieving that field).

回答10:

What kind of object are you using for databinding? Typically I use Collection<T>, List<T>, or Queue<T> (depending on circumstances). These are relatively easy to sort using a custom delegate. See MSDN documentation on the Comparison(T) delegate.

回答11:

var list = ddl.Items.Cast<ListItem>().OrderBy(x => x.Text).ToList();

ddl.DataSource = list;
ddl.DataTextField = "Text";
ddl.DataValueField = "Value"; 
ddl.DataBind();

回答12:

Try it

-------Store Procedure-----(SQL)

USE [Your Database]
GO


CRATE PROC [dbo].[GetAllDataByID]

@ID int


AS
BEGIN
        SELECT * FROM Your_Table
        WHERE ID=@ID
        ORDER BY Your_ColumnName 
END

----------Default.aspx---------

<asp:DropDownList ID="ddlYourTable" runat="server"></asp:DropDownList>

---------Default.aspx.cs-------

protected void Page_Load(object sender, EventArgs e)

{

      if (!IsPostBack)
            {
                List<YourTable> table= new List<YourTable>();

                YourtableRepository tableRepo = new YourtableRepository();

                int conuntryInfoID=1;

                table= tableRepo.GetAllDataByID(ID);

                ddlYourTable.DataSource = stateInfo;
                ddlYourTable.DataTextField = "Your_ColumnName";
                ddlYourTable.DataValueField = "ID";
                ddlYourTable.DataBind();

            }
        }

-------LINQ Helper Class----

public class TableRepository

   {

        string connstr;

        public TableRepository() 
        {
            connstr = Settings.Default.YourTableConnectionString.ToString();
        }

        public List<YourTable> GetAllDataByID(int ID)
        {
            List<YourTable> table= new List<YourTable>();
            using (YourTableDBDataContext dc = new YourTableDBDataContext ())
            {
                table= dc.GetAllDataByID(ID).ToList();
            }
            return table;
        }
    }

回答13:

I agree with the folks in sorting your data in the model before populating them to the DropDownList, so if you are populating this from a DB, it is a good thing to get them sorted already there using a simple order by clause, it will save you some cycles in the web server, and I am sure the DB will do it so much faster. If you are populating this from another data source for example, XML file, using LINQ will be a good idea, or even any variation of Array.Sort will be good.

回答14:

If your data is coming to you as a System.Data.DataTable, call the DataTable's .Select() method, passing in "" for the filterExpression and "COLUMN1 ASC" (or whatever column you want to sort by) for the sort. This will return an array of DataRow objects, sorted as specified, that you can then iterate through and dump into the DropDownList.

回答15:

        List<ListItem> li = new List<ListItem>();
        foreach (ListItem list in DropDownList1.Items)
        {
            li.Add(list);
        }
        li.Sort((x, y) => string.Compare(x.Text, y.Text));
        DropDownList1.Items.Clear();
        DropDownList1.DataSource = li;
        DropDownList1.DataTextField = "Text";
        DropDownList1.DataValueField = "Value";
        DropDownList1.DataBind();

回答16:

To sort an object datasource that returns a dataset you use the Sort property of the control.

Example usage In the aspx page to sort by ascending order of ColumnName

<asp:ObjectDataSource ID="dsData" runat="server" TableName="Data" 
 Sort="ColumnName ASC" />

回答17:

is better if you sort the Source before Binding it to DropDwonList. but sort DropDownList.Items like this:

    Dim Lista_Items = New List(Of ListItem)

    For Each item As ListItem In ddl.Items
        Lista_Items.Add(item)
    Next

    Lista_Items.Sort(Function(x, y) String.Compare(x.Text, y.Text))

    ddl.Items.Clear()
    ddl.Items.AddRange(Lista_Items.ToArray())

(this case i sort by a string(the item's text), it could be the suplier's name, supplier's id)

the Sort() method is for every List(of ) / List<MyType>, you can use it.

回答18:

You can do it this way is simple

private void SortDDL(ref DropDownList objDDL)
{
ArrayList textList = new ArrayList();
ArrayList valueList = new ArrayList();
foreach (ListItem li in objDDL.Items)
{
    textList.Add(li.Text);
}
textList.Sort();
foreach (object item in textList)
{
    string value = objDDL.Items.FindByText(item.ToString()).Value;
    valueList.Add(value);
}
objDDL.Items.Clear();
for(int i = 0; i < textList.Count; i++)
{
     ListItem objItem = new ListItem(textList[i].ToString(), valueList[i].ToString());
     objDDL.Items.Add(objItem);
}

}

And call the method this SortDDL(ref yourDropDownList); and that's it. The data in your dropdownlist will be sorted.

see http://www.codeproject.com/Articles/20131/Sorting-Dropdown-list-in-ASP-NET-using-C#

回答19:

You can use this JavaScript function:

function sortlist(mylist)
{
   var lb = document.getElementById(mylist);
   arrTexts = new Array();
   arrValues = new Array();
   arrOldTexts = new Array();

   for(i=0; i<lb.length; i++)
   {
      arrTexts[i] = lb.options[i].text;
      arrValues[i] = lb.options[i].value;

      arrOldTexts[i] = lb.options[i].text;
   }

   arrTexts.sort();

   for(i=0; i<lb.length; i++)
   {
      lb.options[i].text = arrTexts[i];
      for(j=0; j<lb.length; j++)
      {
         if (arrTexts[i] == arrOldTexts[j])
         {
            lb.options[i].value = arrValues[j];
            j = lb.length;
         }
      }
   }
}

回答20:

Try This:

/// <summary>
/// AlphabetizeDropDownList alphabetizes a given dropdown list by it's displayed text.
/// </summary>
/// <param name="dropDownList">The drop down list you wish to modify.</param>
/// <remarks></remarks>
private void AlphabetizeDropDownList(ref DropDownList dropDownList)
{
    //Create a datatable to sort the drop down list items
    DataTable machineDescriptionsTable = new DataTable();
    machineDescriptionsTable.Columns.Add("DescriptionCode", typeof(string));
    machineDescriptionsTable.Columns.Add("UnitIDString", typeof(string));
    machineDescriptionsTable.AcceptChanges();
    //Put each of the list items into the datatable
    foreach (ListItem currentDropDownListItem in dropDownList.Items) {
            string currentDropDownUnitIDString = currentDropDownListItem.Value;
            string currentDropDownDescriptionCode = currentDropDownListItem.Text;
            DataRow currentDropDownDataRow = machineDescriptionsTable.NewRow();
            currentDropDownDataRow["DescriptionCode"] = currentDropDownDescriptionCode.Trim();
            currentDropDownDataRow["UnitIDString"] = currentDropDownUnitIDString.Trim();
            machineDescriptionsTable.Rows.Add(currentDropDownDataRow);
            machineDescriptionsTable.AcceptChanges();
    }
    //Sort the data table by description
    DataView sortedView = new DataView(machineDescriptionsTable);
    sortedView.Sort = "DescriptionCode";
    machineDescriptionsTable = sortedView.ToTable();
    //Clear the items in the original dropdown list
    dropDownList.Items.Clear();
    //Create a dummy list item at the top
    ListItem dummyListItem = new ListItem(" ", "-1");
    dropDownList.Items.Add(dummyListItem);
    //Begin transferring over the items alphabetically from the copy to the intended drop
     downlist
    foreach (DataRow currentDataRow in machineDescriptionsTable.Rows) {
            string currentDropDownValue = currentDataRow["UnitIDString"].ToString().Trim();
            string currentDropDownText = currentDataRow["DescriptionCode"].ToString().Trim();
            ListItem currentDropDownListItem = new ListItem(currentDropDownText, currentDropDownValue);
    //Don't deal with dummy values in the list we are transferring over
    if (!string.IsNullOrEmpty(currentDropDownText.Trim())) {
        dropDownList.Items.Add(currentDropDownListItem);
    }
}

}

This will take a given drop down list with a Text and a Value property of the list item and put them back into the given drop down list. Best of Luck!

回答21:

If you are adding options to the dropdown one by one without a dataset and you want to sort it later after adding items, here's a solution:

DataTable dtOptions = new DataTable();
DataColumn[] dcColumns = { new DataColumn("Text", Type.GetType("System.String")), 
                           new DataColumn("Value", Type.GetType("System.String"))};
dtOptions.Columns.AddRange(dcColumns);
foreach (ListItem li in ddlOperation.Items)
{
   DataRow dr = dtOptions.NewRow();
   dr["Text"] = li.Text;
   dr["Value"] = li.Value;
   dtOptions.Rows.Add(dr);
}
DataView dv = dtOptions.DefaultView;
dv.Sort = "Text";
ddlOperation.Items.Clear();
ddlOperation.DataSource = dv;
ddlOperation.DataTextField = "Text";
ddlOperation.DataValueField = "Value";
ddlOperation.DataBind();

This would sort the dropdown items in alphabetical order.

回答22:

If you are using a data bounded DropDownList, just go to the wizard and edit the bounding query by:

1. Goto the .aspx page (design view).
2. Click the magic Arrow ">"on the Dropdown List.
3. Select "Configure Data source".
4. Click Next.
5. On the right side of the opened window click "ORDER BY...".
6. You will have up two there field cariteria to sort by. Select the desired field and click OK, then click Finish.

回答23:

You may not have access to the SQL, but if you have the DataSet or DataTable, you can certainly call the Sort() method.