SqlDataSource.FillAsync(IEnumerable<IParameter>, CancellationToken) Method
Populates the SqlDataSource in an asynchronous manner, passes external parameters to the data source, and uses the cancellationToken parameter to send the cancellation signal.
Namespace: DevExpress.DataAccess.Sql
Assembly: DevExpress.DataAccess.v24.2.dll
Declaration
public Task FillAsync(
IEnumerable<IParameter> sourceParameters,
CancellationToken cancellationToken
)Parameters
| Name | Type | Description |
|---|---|---|
| sourceParameters | IEnumerable<IParameter> | External parameters passed to the data source. |
| cancellationToken | CancellationToken | A cancellation token that the task observes. |
Returns
| Type | Description |
|---|---|
| Task | A task that populates the data source. |
Remarks
Use this method to populate an SQL data source in an individual task asynchronously. Unlike the Fill() method call, FillAsync does not lock other actions performed concurrently. For instance, the user interface remains operational while the data source is populated.
Call the FillAsync method with the await operator.
The sourceParameters parameter passes a collection of external parameters to the data source. For instance, you can pass report parameters from a reporting application and use report parameter values to filter data.
The cancellationToken parameter provides a way to send the cancellation signal to the task. The task monitors the token and stops when it receives the signal. Create a CancellationTokenSource class instance and pass its Token property to the FillAsync method call. Call the CancellationTokenSource.Cancel method to stop the task.
All queries are validated one by one. If any validation errors occur, an AggregateException is thrown with these errors. Use the exception’s InnerExceptions property to access a collection of QueryExecutionException objects (use their InnerException property to access an actual ValidationException).
If the validation succeeds, all queries are executed one by one. If any errors occur, an AggregateException is thrown with these errors. Use the exception’s InnerExceptions property to access a collection of QueryExecutionException objects (use their InnerException property to access an actual DevExpress.DataAccess.Native.Sql.SqlExecutionException).
To execute only specific queries, use a FillAsync method overload that accepts the queriesToFill parameter.
Example
The code sample below creates an SqlDataSource, binds the data source query’s catID parameter to the p_catID report parameter, and populates the data source in an asynchronous manner. A CancellationTokenSource class instance is used to allow users to interrupt the data source fill process if it takes too long.
using DevExpress.DataAccess.ConnectionParameters;
using DevExpress.DataAccess.Sql;
using DevExpress.XtraReports.Parameters;
using DevExpress.XtraReports.UI;
using System.Drawing;
// ...
SqlDataSource DataSource { get; set; }
// ...
public XtraReport CreateReportWithParameter()
{
XtraReport report = new XtraReport()
{
Bands = {
new DetailBand() {
Name = "detailBand",
Controls = {
new XRLabel() {
Name = "CategoryID",
BoundsF = new RectangleF(0,0,100,25),
ExpressionBindings = {
new ExpressionBinding("BeforePrint", "Text", "[CategoryID]")
}
},
new XRLabel() {
Name = "CategoryName",
BoundsF = new RectangleF(100,0,200,25),
ExpressionBindings = {
new ExpressionBinding("BeforePrint", "Text", "[CategoryName]")
}
}
}
}
},
};
report.Parameters.Add(new Parameter()
{
Name = "p_catID",
Type = typeof(int),
Value = 3
});
return report;
}
// ...
public void CreateSqlDataSourceWithParameter()
{
MsSqlConnectionParameters connectionParameters = new MsSqlConnectionParameters(
".", "NorthWind", null, null, MsSqlAuthorizationType.Windows);
var sqlDataSource = new SqlDataSource(connectionParameters) { Name = "Sql_Categories" };
var categoriesQuery = SelectQueryFluentBuilder
.AddTable("Categories")
.SelectAllColumnsFromTable()
.Build("Categories");
categoriesQuery.Name = "queryCategories";
QueryParameterInitialization(categoriesQuery);
sqlDataSource.Queries.Add(categoriesQuery);
sqlDataSource.RebuildResultSchema();
DataSource = sqlDataSource;
}
// ...
void QueryParameterInitialization(SelectQuery query)
{
QueryParameter parameter = new QueryParameter()
{
Name = "catID",
Type = typeof(DevExpress.DataAccess.Expression),
Value = new DevExpress.DataAccess.Expression("?p_catID", typeof(System.Int32))
};
query.Parameters.Add(parameter);
query.FilterString = "CategoryID = ?catID";
}
// ...
void AssignDataSourceToReport()
{
XtraReport report = CreateReportWithParameter();
report.DataSource = DataSource;
report.DataMember = "queryCategories";
}
// ...
// Use the cancellationTokenSource to allow users to stop the task.
System.Threading.CancellationTokenSource cancellationTokenSource =
new System.Threading.CancellationTokenSource();
// ...
// A user can click the button to stop the task.
private void cancelButton_Click(object sender, System.EventArgs e)
{
cancellationTokenSource.Cancel();
}
// ...
async void FillDataSourcAsyncWithParametersCancellable(XtraReport report)
{
await DataSource.FillAsync(report.Parameters, cancellationTokenSource.Token);
}