Table of Contents

Attaching / Linking DataSource Objects in C#/Razor Code

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In many cases a DataSource expects data to be passed in. This is usually done by attaching it to another DataSource.

Here is a simple example:

using ToSic.Eav.DataSources;

// A source which can filter by Content-Type (EntityType)
var allAuthors = Kit.Data.GetSource<EntityTypeFilter>(
  attach: App.Data,                     // Use the apps data as input
  parameters: new { TypeName = "Author" }  // tell it to filter by "Author"
);

Note the attach: App.Data. This says "attach App.Data as the input to this DataSource on the stream Default".

Tip

This is the most common way to attach a DataSource to another DataSource.

How Attaching Works

Internally links are created using the IDataSourceLink. The code above simply works, because every DataSource and every DataStream is also a IDataSourceLinkable. This means it has a .Link property which contains the DataSourceLink.

When using the simple linking as specified above, the thing (in this case App.Data) will simply provide it's Default Out-stream as the Default In-stream to the target.

Attaching to/from Another Name

Sometimes you may want to attach to a different stream. There are two Scenarios

  1. Link data from a different Out-Stream (not Default)
  2. Link the data to a different In-Stream (not Default)

Linking to a different Out-Stream

This is done by linking from the desired out-stream. So instead of doing attach: App.Data you would do attach: App.Data["MyStream"].

Linking to a different In-Stream

This is done by renaming the target stream on the link, like this:

attach: App.Data.Link.Rename(inName: "Fallback")

The example above would attach the data not to the Default but to the stream Fallback. The Link property has all the commands needed for renaming etc., which is why you need to add .Link before calling Rename(...).

Tip

The IDataSourceLink API is fluent, functional and immutable. As such anything you write will only affect this use, and not really rename anything.

Attaching Multiple DataSources

Since any .Link provide a link, you can chain multiple links together like this:

// First get the root data source - the App with all data
var appDs2 = Kit.Data.GetAppSource();

// Now create a Type-Filter and tell it to only keep Books / Authors
var books2 = Kit.Data.GetSource<EntityTypeFilter>(attach: appDs2, parameters: new { TypeName = "Books" });
var authors2 = Kit.Data.GetSource<EntityTypeFilter>(attach: appDs2, parameters: new { TypeName = "Persons" });

// The following lines are just spread for easier documentation
// Usually you would write in inline
var dataSourceLinks2 = books2.Link    // Get the link to the books
  .Add(authors2.Link              // Add the author2 link
    .Rename(inName: "Stream2"     // but rename the link so it's attached as "Stream2"
  )
);
var merged2 = Kit.Data.GetSource<StreamMerge>(attach: dataSourceLinks2);

History

  1. Introduced in 2sxc 16.00
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