GetQueryableEventArgs.Tag Property
Gets or sets an arbitrary object associated with a queryable source.
Namespace: DevExpress.Data.Linq
Assembly: DevExpress.Data.v24.1.dll
NuGet Package: DevExpress.Data
Declaration
Property Value
Type | Description |
---|---|
Object | An object associated with a queryable source. |
Remarks
Use this property in a LinqInstantFeedbackSource.GetQueryable event handler to pass an arbitrary object, along with a queryable source supplied via the GetQueryableEventArgs.QueryableSource property. The object will also be passed to a LinqInstantFeedbackSource.DismissQueryable event handler, so that you can dispose of it when the queryable source is no longer required for the LinqInstantFeedbackSource. For instance, you can assign the Tag property a DataContext, instantiated within a LinqInstantFeedbackSource.GetQueryable event handler, and then dispose of the DataContext within a LinqInstantFeedbackSource.DismissQueryable event handler, as shown below.
Example
This example demonstrates how to initialize a LinqInstantFeedbackSource, to retrieve data from a “Purchasing.PurchaseOrderHeader” data table (included in the AdventureWorks database shipped with MS SQL Server). The PurchaseOrderHeader persistent class is declared, and mapped to the “Purchasing.PurchaseOrderHeader” data table using the System.Data.Linq.Mapping.TableAttribute attribute. Then, a System.Data.Linq.Table<PurchaseOrderHeader> is passed to the LinqInstantFeedbackSource in the LinqInstantFeedbackSource.GetQueryable event handler.
using System.ComponentModel;
using System.Data.Linq;
using System.Data.Linq.Mapping;
using DevExpress.Data.Linq;
// The class describing the "Purchasing.PurchaseOrderHeader" table
// from the AdventureWorks SQL database
[Table(Name="Purchasing.PurchaseOrderHeader")]
public partial class PurchaseOrderHeader : INotifyPropertyChanging, INotifyPropertyChanged {
//...
[Column(Storage="_PurchaseOrderID", AutoSync=AutoSync.OnInsert,
DbType="Int NOT NULL IDENTITY",
IsPrimaryKey=true, IsDbGenerated=true)]
// The property mapped to the primary key column
public int PurchaseOrderID {
//...
}
//...
}
// The class describing the AdventureWorks SQL database
[DatabaseAttribute(Name="AdventureWorks")]
public partial class AdvWorksDataContext : DataContext {
//...
public System.Data.Linq.Table<PurchaseOrderHeader> PurchaseOrderHeaders {
get {
return this.GetTable<PurchaseOrderHeader>();
}
}
//...
}
public partial class Form1 : Form {
//...
private void Form1_Load(object sender, EventArgs e) {
// Specify the key property of the PurchaseOrderHeader
linqInstantFeedbackSource1.KeyExpression = "PurchaseOrderID";
// Handle the GetQueryable event, to create a DataContext and assign a queryable source
linqInstantFeedbackSource1.GetQueryable += linqInstantFeedbackSource1_GetQueryable;
// Handle the DismissQueryable event, to dispose of the DataContext
linqInstantFeedbackSource1.DismissQueryable += linqInstantFeedbackSource1_DismissQueryable;
// Assign the created data source to an XtraGrid
gridControl1.DataSource = linqInstantFeedbackSource1;
}
void linqInstantFeedbackSource1_GetQueryable(object sender, GetQueryableEventArgs e) {
// Instantiate a new DataContext
AdvWorksDataContext dataContext = new AdvWorksDataContext();
// Assign a queryable source to the LinqInstantFeedbackSource
e.QueryableSource = dataContext.PurchaseOrderHeaders;
// Assign the DataContext to the Tag property,
// to dispose of it in the DismissQueryable event handler
e.Tag = dataContext;
}
void linqInstantFeedbackSource1_DismissQueryable(object sender, GetQueryableEventArgs e) {
// Dispose of the DataContext
((AdvWorksDataContext)e.Tag).Dispose();
}
}
Related GitHub Examples
The following code snippet (auto-collected from DevExpress Examples) contains a reference to the Tag property.
Note
The algorithm used to collect these code examples remains a work in progress. Accordingly, the links and snippets below may produce inaccurate results. If you encounter an issue with code examples below, please use the feedback form on this page to report the issue.