LinqInstantFeedbackSource.DismissQueryable Event
Occurs when the LinqInstantFeedbackSource no longer needs the queryable source it used to retrieve objects from the data store.
Namespace: DevExpress.Data.Linq
Assembly: DevExpress.Data.v18.1.dll
Declaration
Event Data
The DismissQueryable event's data class is GetQueryableEventArgs. The following properties provide information specific to this event:
| Property | Description |
|---|---|
| AreSourceRowsThreadSafe | Specifies whether elements retrieved by the LinqInstantFeedbackSource‘s queryable source are thread-safe. |
| KeyExpression | Gets or sets the name of the key property. |
| QueryableSource | Gets or sets the queryable data source. |
| Tag | Gets or sets an arbitrary object associated with a queryable source. |
Remarks
You can access the object you have assigned to the GetQueryableEventArgs.Tag property in the LinqInstantFeedbackSource.GetQueryable event handler.
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 snippets (auto-collected from DevExpress Examples) contain references to the DismissQueryable event.
Note
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