LookUpEdit Class
A text box editor with a dropdown panel that displays data in a simple table layout.
Namespace: DevExpress.XtraEditors
Assembly: DevExpress.XtraEditors.v24.2.dll
Declaration
Related API Members
The following members return LookUpEdit objects:
Remarks
Lookups are data-bound editors that display data source records in their dropdowns. Users can select one item (record) at a time. Users cannot edit records in the dropdown.
The following image shows the DevExpress WinForms Lookup.
The DevExpress WinForms Subscription includes four lookup controls:
LookUpEdit- GridLookUpEdit – A lookup editor that embeds the Data Grid within the dropdown.
- SearchLookUpEdit – A grid-based lookup with an embedded Find Panel.
- TreeListLookUpEdit – A lookup editor that embeds the Tree List control within the dropdown.
Read the following topic to see the difference: Lookup Feature Matrix.
Bind to Data
A lookup is a data-bound control. Use the following properties to bind a lookup editor to a data source:
- DataSource – Specifies the source of records.
- DisplayMember – The data source field, whose values are visible to users. A value from this field is displayed in the lookup’s text box when a user selects a record.
- ValueMember – The data source field with unique/key values. A value from this data field is assigned to the lookup’s
EditValueproperty when a user selects a record. - KeyMember – Specifies the name of a key field (or multiple key fields). Use this property in Advanced Lookup Binding Mode.
Important
When a lookup editor is used to edit cell values in the Data Grid, the type of the ValueMember field must match the type of the field assigned to the grid’s lookup column (GridColumn.FieldName). Enable the lookup’s ThrowExceptionOnInvalidLookUpEditValueType option to detect data type issues.
Read the following topics for detailed information and examples:
- Lookup - Standard Binding (Simple Data Types)
- Lookup - Advanced Binding (Business Objects)
- Lookup - Bind to a Dictionary
How to Bind a Lookup to Data
The following example shows how to bind a lookup editor to data created at runtime:
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
public partial class Form1 : DevExpress.XtraEditors.XtraForm {
public Form1() {
InitializeComponent();
// Binds the lookup to data.
lookUpEdit1.Properties.DataSource = Employee.GetSampleData();
// Sets the lookup's data fields.
lookUpEdit1.Properties.DisplayMember = "FullName";
lookUpEdit1.Properties.ValueMember = "ID";
// Sets the lookup's value. Selects the first record.
lookUpEdit1.EditValue = 0;
}
}
public class Employee {
public Employee(int iD, string firstName, string lastName) {
ID = iD;
FirstName = firstName;
LastName = lastName;
}
public static List<Employee> GetSampleData() {
return new List<Employee>() {
new Employee(0, "Bart", "Arnaz"),
new Employee(1, "Leah", "Simpson"),
new Employee(2, "Arnold", "Schwartz"),
new Employee(3, "William", "Zimmer"),
new Employee(4, "Samantha", "Piper")
};
}
// The 'ID' field must contain unique values.
public int ID { get; private set; }
public string FirstName { get; set; }
public string LastName { get; set; }
[Display(Order = -1)]
public string FullName {
get {
return string.Format("{0} {1}", FirstName, LastName);
}
}
}
The image below shows the result.
Cascading Lookups
Lookups can filter their values based on the currently selected values of other lookups. See the following examples for detailed information:
- How to Implement Standalone Cascading Lookups
- How to Implement Cascading Lookups within Data Grid Control (In-Place Mode)
Lookup Settings
The following table lists the most popular settings:
Property | Description |
|---|---|
Gets or sets the lookup’s value. | |
Specifies whether users can type in the lookup’s text box. Set the | |
Specifies the “best-fit” mode for lookup columns in the dropdown window. This feature proportionally resizes all columns to fit cell contents. | |
Specifies a string that is displayed in the text box when the lookup’s value is null (for example, | |
If enabled, users can press | |
Use this property to access a collection of lookup columns. | |
Creates lookup columns for all fields in the data source. | |
Lookups can display columns that are not bound to data source fields. Handle the | |
Gets or sets the width of the dropdown window (in pixels). Use the PopupWidthMode property to specify whether the dropdown’s default width matches the width of the lookup or dropdown content. | |
Specifies the dropdown’s height (in rows). Use the DropDownItemHeight property to specify the height of a row (in pixels). | |
Gets or sets the lookup editor whose value determines the filter criteria applied to the popup data source of the current lookup editor. | |
Gets or sets the name(s) of the foreign key field(s) by which the popup data source of the lookup editor is filtered. The field must be editable and accept new values (read-only fields are not supported). | |
Enable this option to display the dropdown immediately after a user has typed a character in the text box. | |
Specifies the search mode (Auto-Complete, Auto-Filter, AutoSuggest, AutoSearch, etc.). | |
Specifies a column against which a lookup performs the incremental search in | |
Gets or sets whether to enable the multiple item selection and specifies how the EditValue property stores selected items. |
Item Search
Set the SearchMode property to SearchMode.AutoSuggest or SearchMode.AutoSearch to enable item search. The lookup automatically sets the TextEditStyle property to Standard when you select either of these modes.
The difference between AutoSearch and AutoSuggest modes is as follows:
- AutoSuggest runs a custom Task to return a collection of items and display them in the lookup’s dropdown. The lookup gets a virtual data source that updates every time a user inputs a new value. Use this mode in unbound lookups.
- AutoSearch utilizes the built-in search algorithm to find items that meet the specified criteria in a data source.
- AutoSearch mode is not supported by server-mode sources.
- Both search modes are available for stand-alone lookups only.
Handle the PopupFilter event to specify a custom filter expression.
using DevExpress.Data.Filtering;
using DevExpress.XtraEditors.Controls;
private void LookUpEdit1_PopupFilter(object sender, PopupFilterEventArgs e)
{
e.Criteria = CriteriaOperator.Parse(string.Format("DeliveryDate < '{0}'", DateTime.Today));
}
AutoSuggest Mode
When a user types text, the editor fires the AutoSuggest event (LookUpEdit.AutoSuggest / GridLookUpEdit.AutoSuggest) that runs a custom asynchronous task (a System.Threading.Tasks.Task object). This task performs a search against the given data set, and returns the ICollection object with records that match the entered text. This collection is automatically assigned to the editor’s DataSource and its entries appear in the editor drop-down menu.
Note
If an editor has an assigned data source, the editor switches to AutoSearch mode and fires the AutoSearch event.
This feature is in effect only for stand-alone editors.
AutoSuggest event parameters include:
QuerySuggestions — Assign a Task that performs the search and returns the suggestions collection.
Text — Returns the entered user text.
SetMinimumAnimationDuration — While a Task is searching for suggestions, the editor displays a loading indicator. To prevent this indicator from flickering when the search completes too quickly, the SetMinimumAnimationDuration method allows you to set the minimum on-screen duration.
SetHighlightRanges — Allows you to manually choose which parts of found items should be highlighted.
To test the AutoSuggest mode, run the AutoSuggest Lookup Demo Center module. You can click the “Open Solution” Ribbon button to view the complete demo code.
In this demo, suggestions (drop-down menu items) are retrieved on the QueryAsync task. The SetMinimumAnimationDuration method ensures the loading indicator is visible for at least one second.
lookUpEdit1.AutoSuggest += OnAutoSuggest;
void OnAutoSuggest(object sender, LookUpEditAutoSuggestEventArgs e) {
// Set delay (if needed)
e.SetMinimumAnimationDuration(TimeSpan.FromMilliseconds(1000));
// Assign a Task that returns suggestions
e.QuerySuggestions = WorldCities.QueryAsync(e.Text, e.CancellationToken);
}
The code below demonstrates how this QueryAsync Task is implemented. The EnsureAllEntries method retrieves all locations from the source. If a user opens the editor drop-down menu, all entries are visible. Otherwise, the method compares user text with data source records.
public static Task<ICollection> QueryAsync(string text, CancellationToken cancellation) {
var contains = IgnoreCaseComparisonFunctions.GetContains(
CultureInfo.CurrentCulture.CompareInfo, CompareOptions.IgnoreCase);
return Task.Run(() => {
var entries = CsvDataHelper.EnsureAllEntries();
var parts = text.Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
if(parts.Length == 0)
return entries as ICollection;
else
return entries.Where(e => {
// Stop task if needed
cancellation.ThrowIfCancellationRequested();
return parts.All(x => e.Tags.Any(tag => contains(tag, x)));
}).ToList() as ICollection;
});
}
In this demo, the data source is the “Data\cities.csv” Excel file that stores approximately 13,000 city names. Each record also contains country and state names, country UN code, and Unicode city name. All records are extracted inside the custom Entry class.
public sealed class Entry {
readonly static List<Entry> allEntries = new List<Entry>();
public static IEnumerable<Entry> EnsureAllEntries() {
lock(allEntries) {
if(allEntries.Count == 0 && File.Exists("Data\cities.csv")) {
var lines = File.ReadLines("Data\cities.csv").Skip(1);
var entries = lines.Select(x => new Entry(x))
.OrderBy(e => e.Country)
.ThenBy(e => e.City);
foreach(Entry entry in entries)
allEntries.Add(entry);
}
return allEntries;
}
}
//. . .
}
The Entry class contains data fields for Excel file columns, plus additional data fields for values combined from standard fields.
Tags- a portion of a record to be checked against an entered user text: City, Unicode City Name, and State Name;Text- full location address in the “CountryName, CityName, StateName” format.HtmlText- same asText, but country name is displayed with grayed-out text. This field is used to custom draw lookup items (see the “Additional Customization” section below).
public sealed class Entry {
//standard fields
public string Country { get; private set; }
public string City { get; private set; }
public string City_Unicode { get; private set; }
public string Admin_Name_Unicode { get; private set; }
public string Country_UN { get; private set; }
//additional fields
public string[] Tags { get; private set; }
public string Text { get; private set; }
public string HtmlText { get; private set; }
}
You can call the LookUpEditBase.StartAutoSuggest method to manually trigger the AutoSuggest event.
Custom Item Draw
The HtmlText property declared in the Entry class is optional - it is not required to implement the auto-suggest functionality. This property is used to manually re-paint lookup items so that country names appear washed out. To do that, handle the RepositoryItemLookUpEdit.CustomDrawCell event.
lookUpEdit1.CustomDrawCell += OnCustomDrawCell;
void OnCustomDrawCell(object sender, LookUpCustomDrawCellArgs e) {
e.DrawHtmlText(WorldCities.GetHtmlText(e.Row));
e.Handled = true;
}
Custom Highlight Ranges
The QueryAsync Task compares user text with the entry Tags property. This property includes city name, city unicode name, and state name - country names are ignored. For example, the figure below illustrates that the demo database contains many Mexican cities.
If a user enters “ex”, from all Mexican cities only “Mexicali” and “Mexico City” remain visible - the Task behaves correctly and filters out non-matching records. However, although the Task ignores countries, the editor highlights “ex” in country names as well.
This happens because there are two separate processes that take place in a lookup editor.
- A Task assigned to the QuerySuggestions property scans the data source and chooses records to show in a drop-down menu.
- A lookup editor scans items returned by the Task, and looks for user text matches.
If these two processes use different algorithms, a misleading highlight behavior similar to that mentioned above may happen. If this happens, define custom highlight range(s) with the SetHighlightRange / SetHighlightRanges methods. The demo code below uses the same logic as in the QueryAsync task to display the correct ranges.
void OnAutoSuggest(object sender, LookUpEditAutoSuggestEventArgs e) {
//...
// Set Custom Highlight Strategy
e.SetHighlightRanges(HighlightTags(e.Text));
}
static Func<string, string, DisplayTextHighlightRange[]> HighlightTags(string pattern) {
var indexOf = IgnoreCaseComparisonFunctions.GetIndexOf(
CultureInfo.CurrentCulture.CompareInfo, CompareOptions.IgnoreCase);
var parts = pattern.Split(new char[] { ' ' },
StringSplitOptions.RemoveEmptyEntries);
return (displayText, fieldName) => {
var tags = displayText.Split(new string[] { ", " },
StringSplitOptions.RemoveEmptyEntries);
var ranges = new List<DisplayTextHighlightRange>();
for(int i = 1/*skip country tag*/; i < tags.Length; i++) {
int tagStart = displayText.IndexOf(tags[i]);
for(int j = 0; j < parts.Length; j++) {
int index = indexOf(tags[i], parts[j]);
if(index != -1)
ranges.Add(new DisplayTextHighlightRange(tagStart + index, parts[j].Length));
}
}
return ranges.ToArray();
};
}
The AutoSuggest event parameter offers a number of methods that you can use to define custom highlight ranges.
- HighlightAny - selects every item caption part that matches the given text.
- HighlightFirst - selects the first text entry.
- HighlightFromStart - selects the first N characters of item captions.
AutoSearch Mode
The AutoSearch mode allows users to search for required data source items.
Change Search Logic
Handle the AutoSearch event (LookUpEdit.AutoSearch \ GridLookUpEdit.AutoSearch) and use a SetParameters method overload to specify how the editor should compare user text with editor items.
- parserKind parameter - specifies how user text parts divided by a space character should be combined (see the ColumnViewOptionsFind.ParserKind property for examples).
- condition parameter - specifies which function should be used to build filter expressions (see the ColumnViewOptionsFind.Condition Data Grid property for examples).
- field or fields[] parameter - allows you to limit the search by specific data fields only.
- text parameter - allows you to replace the user text.
The example below illustrates how to make the editor look for items whose text starts with the user text.
lookUpEdit1.AutoSearch += OnAutoSearch;
void OnAutoSearch(object sender, LookUpEditAutoSearchEventArgs e) {
string[] fields = new string[] { "ShipCity", "ShipCountry" };
e.SetParameters(fields, e.Text, FindPanelParserKind.And, FilterCondition.StartsWith);
}
You can call the LookUpEditBase.StartAutoSearch method to manually trigger the AutoSearch event.
Custom Text Highlight Ranges
Lookup editors highlight text portions that match user text. Handle the AutoSearch event to implement custom highlight ranges. This mode uses same highlight API as the AutoSuggest mode does.
The example below illustrates how to make a lookup editor highlight the entire field value if it starts with the specified user text.
private void LookUpEdit1_AutoSearch(object sender, LookUpEditAutoSearchEventArgs e)
{
e.SetAutoSearchParameters(FindPanelParserKind.And, FilterCondition.StartsWith);
e.SetHighlightRanges(CustomHightlight(e.Text));
}
static Func<string, string, DisplayTextHighlightRange[]> CustomHightlight(string userText)
{
return (displayText, fieldName) =>
{
if (fieldName == "ShipCity" || fieldName == "ShipCountry")
{
if (displayText.StartsWith(userText))
return new DisplayTextHighlightRange[] {
new DisplayTextHighlightRange(0, displayText.Length) };
}
return null;
};
}
Examples
How to Use a LookUpEdit as an In-Place Editor for Data Grid
The following example demonstrates how to create and customize an in-place LookUpEdit control (RepositoryItemLookUpEdit) to edit cell values in the CategoryID column.
The lookup editor displays category names in the edit box instead of category IDs (see the DisplayMember setting).
Play the animation to see the result:
using DevExpress.XtraEditors.Repository;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace LookupEdit_StandardBinding {
public partial class Form1 : Form {
public Form1() {
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e) {
InitData();
gridControl1.DataSource = Products;
gridView1.Columns["UnitPrice"].DisplayFormat.FormatType = DevExpress.Utils.FormatType.Numeric;
gridView1.Columns["UnitPrice"].DisplayFormat.FormatString = "c2";
// Create an in-place LookupEdit control.
RepositoryItemLookUpEdit riLookup = new RepositoryItemLookUpEdit();
riLookup.DataSource = Categories;
riLookup.ValueMember = "ID";
riLookup.DisplayMember = "CategoryName";
// Enable the "best-fit" functionality mode in which columns have proportional widths and the popup window is resized to fit all the columns.
riLookup.BestFitMode = DevExpress.XtraEditors.Controls.BestFitMode.BestFitResizePopup;
// Specify the dropdown height.
riLookup.DropDownRows = Categories.Count;
// Enable the automatic completion feature. In this mode, when the dropdown is closed,
// the text in the edit box is automatically completed if it matches a DisplayMember field value of one of dropdown rows.
riLookup.SearchMode = DevExpress.XtraEditors.Controls.SearchMode.AutoComplete;
// Specify the column against which an incremental search is performed in SearchMode.AutoComplete and SearchMode.OnlyInPopup modes
riLookup.AutoSearchColumnIndex = 1;
// Optionally hide the Description column in the dropdown.
// riLookup.PopulateColumns();
// riLookup.Columns["Description"].Visible = false;
gridControl1.RepositoryItems.Add(riLookup);
// Assign the in-place LookupEdit control to the grid's CategoryID column.
// Note that the data types of the "ID" and "CategoryID" fields match.
gridView1.Columns["CategoryID"].ColumnEdit = riLookup;
gridView1.BestFitColumns();
}
List<Product> Products = new List<Product>();
List<Category> Categories = new List<Category>();
private void InitData() {
Products.Add(new Product() { ProductName = "Sir Rodney's Scones", CategoryID = 3, UnitPrice = 10 });
Products.Add(new Product() { ProductName = "Gustaf's Knäckebröd", CategoryID = 5, UnitPrice = 21 });
Products.Add(new Product() { ProductName = "Tunnbröd", CategoryID = 5, UnitPrice = 9 });
Products.Add(new Product() { ProductName = "Guaraná Fantástica", CategoryID = 1, UnitPrice = 4.5m });
Products.Add(new Product() { ProductName = "NuNuCa Nuß-Nougat-Creme", CategoryID = 3, UnitPrice = 14 });
Products.Add(new Product() { ProductName = "Gumbär Gummibärchen", CategoryID = 3, UnitPrice = 31.23m });
Products.Add(new Product() { ProductName = "Rössle Sauerkraut", CategoryID = 7, UnitPrice = 45.6m });
Products.Add(new Product() { ProductName = "Thüringer Rostbratwurst", CategoryID = 6, UnitPrice = 123.79m });
Products.Add(new Product() { ProductName = "Nord-Ost Matjeshering", CategoryID = 8, UnitPrice = 25.89m });
Products.Add(new Product() { ProductName = "Gorgonzola Telino", CategoryID = 4, UnitPrice = 12.5m });
Categories.Add(new Category() { ID = 1, CategoryName = "Beverages", Description = "Soft drinks, coffees, teas, beers, and ales" });
Categories.Add(new Category() { ID = 2, CategoryName = "Condiments", Description = "Sweet and savory sauces, relishes, spreads, and seasonings" });
Categories.Add(new Category() { ID = 3, CategoryName = "Confections", Description = "Desserts, candies, and sweet breads" });
Categories.Add(new Category() { ID = 4, CategoryName = "Dairy Products", Description = "Cheeses" });
Categories.Add(new Category() { ID = 5, CategoryName = "Grains/Cereals", Description = "Breads, crackers, pasta, and cereal" });
Categories.Add(new Category() { ID = 6, CategoryName = "Meat/Poultry", Description = "Prepared meats" });
Categories.Add(new Category() { ID = 7, CategoryName = "Produce", Description = "Dried fruit and bean curd" });
Categories.Add(new Category() { ID = 8, CategoryName = "Seafood", Description = "Seaweed and fish" });
}
}
public class Product {
public string ProductName { get; set; }
public decimal UnitPrice { get; set; }
public int CategoryID { get; set; }
}
public class Category {
public int ID { get; set; }
public string CategoryName { get; set; }
public string Description { get; set; }
}
}
How to Display SVG Icons in Dropdown
This example demonstrates how to display SVG icons from the SvgImageCollection within the LookUp editor’s dropdown.
using System;
using System.Collections.Generic;
using DevExpress.Utils;
using DevExpress.Utils.Svg;
public partial class Form1 : DevExpress.XtraEditors.XtraForm {
public Form1() {
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e) {
lookUpEdit1.Properties.AllowNullInput = DefaultBoolean.True;
lookUpEdit1.Properties.DataSource = InitData();
lookUpEdit1.Properties.ValueMember = "ID";
lookUpEdit1.Properties.DisplayMember = "DocumentFormat";
}
List<DataObject> InitData() {
return new List<DataObject>() {
new DataObject(0, "MS Word Binary File Format") { SvgImage = svgImageCollection1[0] },
new DataObject(1, "Portable Document Format") { SvgImage = svgImageCollection1[1] },
new DataObject(2, "Microsoft Excel Spreadsheet") { SvgImage = svgImageCollection1[2] },
new DataObject(3, "Extensible Markup Language") { SvgImage = svgImageCollection1[3] }
};
}
}
public class DataObject {
int fId;
public DataObject(int fId, string format) {
this.fId = fId;
DocumentFormat = format;
}
public int ID {
get { return fId; }
}
public SvgImage SvgImage { get; set; }
public string DocumentFormat { get; set; }
}
How to Obtain a Value of a Cell Inside a Focused Row
When a LookUpEdit’s EditValue property changes, you may need to read the value of a cell located at the intersection of a selected row and a specific column. To do this, handle the LookUpEdit.EditValueChanged event and call the GetColumnValue(String) method.
private void lookUpEdit1_EditValueChanged(object sender, EventArgs e) {
DevExpress.XtraEditors.LookUpEdit editor = sender as DevExpress.XtraEditors.LookUpEdit;
object value = editor.GetColumnValue("aFieldName");
}
You may also call the GetDataSourceRowByKeyValue(Object) method instead of GetColumnValue. This method retrieves row objects of a data source assigned to the editor’s Properties.DataSource property. For example, if your editor is bound to a DataTable object, use the code below.
private void lookUpEdit1_EditValueChanged(object sender, System.EventArgs e) {
DevExpress.XtraEditors.LookUpEdit editor = sender as DevExpress.XtraEditors.LookUpEdit;
DataRowView row = editor.Properties.GetDataSourceRowByKeyValue(editor.EditValue) as DataRowView;
object value = row["aFieldName"];
}
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