Dictionary as a Data Source for a Lookup Editor

• Mar 05, 2021
• 4 minutes to read

If you use a Dictionary<TKey,TValue> as a data source for a lookup editor, the editor uses keys and values as follows:

• the TKey values — as actual values. These values are assigned to the editor when a user selects an item in the drop-down box.
• the TValue values — as string representations of the actual values. These strings are displayed in the edit box and drop-down window.

There is no need to specify the ValueMember and DisplayMember properties.

Note

The TKey and TValue parameters should be of the String type or a value type. For example, keys are integers and values are strings.

The example below uses a Dictionary<TKey,TValue> that contains category identifiers and names.

C#

using System.Collections.Generic;

Dictionary<int, string> categories = new Dictionary<int, string>();
categories.Add(0, "Beverages");
categories.Add(1, "Grains");
categories.Add(2, "Seafood");

VB.NET

Imports System.Collections.Generic

Dim categories As Dictionary(Of Integer, String) = New Dictionary(Of Integer, String)()
categories.Add(0, "Beverages")
categories.Add(1, "Grains")
categories.Add(2, "Seafood")
LookUpEdit1.Properties.DataSource = categories

Note that the editor displays a single column, which contains string representations. The column that contains values is hidden.

The Columns property provides access to the column collection. You can use the Key and Value names to retrieve columns in code. The code below shows how to display the Key column and align values in the Value column at the far edge. To specify whether a column is displayed, use the Visible property.

C#

using DevExpress.Utils;

lookUpEdit1.Properties.ForceInitialize();
lookUpEdit1.Properties.PopulateColumns();
lookUpEdit1.Properties.Columns["Key"].Visible = true;
lookUpEdit1.Properties.Columns["Value"].Alignment = HorzAlignment.Far;

VB.NET

Imports DevExpress.Utils

lookUpEdit1.Properties.ForceInitialize()
lookUpEdit1.Properties.PopulateColumns()
lookUpEdit1.Properties.Columns("Key").Visible = True
lookUpEdit1.Properties.Columns("Value").Alignment = HorzAlignment.Far

Example

In the example below, a grid uses a lookup editor to display and edit values in the Category ID column. The editor is bound to a Dictionary<TKey,TValue> that contains category identifiers and names. The column actually contains integer identifiers but the editor displays category names.

View Example

Form1.cs

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_Dictionary {
    public partial class Form1 : Form {
        public Form1() {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e) {

            gridControl1.DataSource = new List<Product> {
                new Product(){ ProductName="Chang", CategoryID =  0  },
                new Product(){ ProductName="Ipoh Coffee", CategoryID =  0  },
                new Product(){ ProductName="Ravioli Angelo", CategoryID = 1  },
                new Product(){ ProductName="Filo Mix", CategoryID = 1  },
                new Product(){ ProductName="Tunnbröd", CategoryID  = 1  },
                new Product(){ ProductName="Konbu", CategoryID  = 2  },
                new Product(){ ProductName="Boston Crab Meat", CategoryID  = 2  }
            };

            Dictionary<int, string> Categories = new Dictionary<int, string>();
            Categories.Add(0, "Beverages");
            Categories.Add(1, "Grains");
            Categories.Add(2, "Seafood");

            RepositoryItemLookUpEdit riLookUp = new RepositoryItemLookUpEdit();
            riLookUp.DataSource = Categories;
            // Change the column caption.
            riLookUp.PopulateColumns();
            riLookUp.Columns["Value"].Caption = "Name";

            gridControl1.RepositoryItems.Add(riLookUp);
            gridView1.Columns["CategoryID"].ColumnEdit = riLookUp;
        }
    }

    public class Product {
        public int CategoryID { get; set; }
        public string ProductName { get; set; }
    }


}

Form1.vb

Imports DevExpress.XtraEditors.Repository
Imports System
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Data
Imports System.Drawing
Imports System.Linq
Imports System.Text
Imports System.Threading.Tasks
Imports System.Windows.Forms

Namespace LookUpEdit_Dictionary
    Partial Public Class Form1
        Inherits Form

        Public Sub New()
            InitializeComponent()
        End Sub

        Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs) Handles MyBase.Load

            gridControl1.DataSource = New List(Of Product) From { _
                New Product() With {.ProductName="Chang", .CategoryID = 0}, _
                New Product() With {.ProductName="Ipoh Coffee", .CategoryID = 0}, _
                New Product() With {.ProductName="Ravioli Angelo", .CategoryID = 1}, _
                New Product() With {.ProductName="Filo Mix", .CategoryID = 1}, _
                New Product() With {.ProductName="Tunnbröd", .CategoryID = 1}, _
                New Product() With {.ProductName="Konbu", .CategoryID = 2}, _
                New Product() With {.ProductName="Boston Crab Meat", .CategoryID = 2} _
            }

            Dim Categories As New Dictionary(Of Integer, String)()
            Categories.Add(0, "Beverages")
            Categories.Add(1, "Grains")
            Categories.Add(2, "Seafood")

            Dim riLookUp As New RepositoryItemLookUpEdit()
            riLookUp.DataSource = Categories
            ' Change the column caption.
            riLookUp.PopulateColumns()
            riLookUp.Columns("Value").Caption = "Name"

            gridControl1.RepositoryItems.Add(riLookUp)
            gridView1.Columns("CategoryID").ColumnEdit = riLookUp
        End Sub
    End Class

    Public Class Product
        Public Property CategoryID() As Integer
        Public Property ProductName() As String
    End Class


End Namespace