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These documentations are for versions before 15.x. They don't apply to v15+ but are kept for reference. We highly recommend that you don't use them.

DataSource API: Provide(...)

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DataSources always provide data on an Out Stream. The Provide method makes it very easy to do.

How to use Provide

In general, you need

  1. a method like GetList() which returns an IEnumerable<IEntity>
  2. attach that stream to the Out - usually on a stream called Default

Here's a simple example of the constructor of the Tutorial Basic DataSource, which provides the default stream:

/// <summary>
/// Constructor to tell the system what out-streams we have
/// </summary>
public DateTimeDataSourceBasic()
{
  Provide(GetList); // "Default" out; when accessed, will deliver GetList
}

/// <summary>
/// Get-List method, which will load/build the items once requested 
/// Note that the setup is lazy-loading so this code will only execute when used
/// </summary>
private ImmutableArray<IEntity> GetList()
{
  var date = DateTime.Now;
  var values = new Dictionary<string, object>
  {
      {DateFieldName, date},
      {"Weekday", date.DayOfWeek},
      {"DayOfWeek", (int) date.DayOfWeek}
  };
  
  // Construct the IEntity and return as ImmutableArray
  var entity = DataBuilder.Entity(values, titleField: DateFieldName);
  return new [] {entity}.ToImmutableArray();
}

This example ensures that the .Out["Default"] as well as the .List (which is a shorthand for .Out[Constants.DefaultStreamName].List) are mounted, ready to deliver.

Overloads

  • Provide(listfunction) - default version, which provides the "Default" stream
  • Provide(name, listfunction) - alternative for named streams when your DataSource has more streams.

Providing multiple streams

In case you want to offer multiple streams (like one containing products, the other categories), the common pattern is:

public SomeConstructor()
{
    Provide(GetProducts);
    Provide("Categories", GetCategories);

    // ...
}

Performance Notes

It's important to know that Provide simply prepares the Out for use, but will not call the inner function unless this stream is requested. This makes DataSources very performant, as no code is run which isn't needed.

Read also

  • todo

History

  1. Introduced in EAV 4.x, 2sxc 09.13
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