HelperFirstObjT Method

public static ObjT First<ObjT>(
	this H5Group root,
	string key = null,
	bool recursive = true,
	bool includeAttributes = false,
	Predicate<ObjT> predicate = null
)
where ObjT : H5Object

<ExtensionAttribute>
Public Shared Function First(Of ObjT As H5Object) ( 
	root As H5Group,
	Optional key As String = Nothing,
	Optional recursive As Boolean = true,
	Optional includeAttributes As Boolean = false,
	Optional predicate As Predicate(Of ObjT) = Nothing
) As ObjT

Dim root As H5Group
Dim key As String
Dim recursive As Boolean
Dim includeAttributes As Boolean
Dim predicate As Predicate(Of ObjT)
Dim returnValue As ObjT

returnValue = root.First(key, recursive, 
	includeAttributes, predicate)

Parameters

root

Type: ILNumerics.IO.HDF5H5Group
the current root node of the set of children to search in

key (Optional)

Type: SystemString
[optional] if specified: the search term to filter the Name of the objects; default: match any name

recursive (Optional)

Type: SystemBoolean
[optional] true: search for the object recursively in the children of the current group. Default: true

includeAttributes (Optional)

Type: SystemBoolean
[optional] true: consider attributes as regular nodes, apply any matching rules to them; default: false

predicate (Optional)

Type: SystemPredicateObjT
[optional] if specified: the filter function used to determine a match; default: match any object

Type Parameters

ObjT

The (H5-) type of the object to search and return

Return Value

Usage Note

This method allows the efficient retrieval of a specific object from a tree of H5Objects. The optional filter arguments may be used in order to delimit the set of considered objects. If used without any optional filter rules, First() returns the first object within the group or its children, which matches the type ObjT.

First() returns null, if no matching object was found.

No slashes are allowed for key.

Search order: if recursive is false, the children of the group are searched in the increasing order of their (HDF5) indices. That index is assigned by the HDF5 library at the time, the object was created in the file and added to the group. If recursive is true the subtree below root is traversed in breadth-first order, i.e.: the children of group are visited first, afterwards the children of the children a.s.o.

First() is based on Find() which does currently not handle cyclic references! Using First() on files which contain cyclic references may cause infinitely looping over the cycle, hence does not return anything!

[ILNumerics HDF5 Module]

using (var file = new H5File("example.h5")) {
    var dset = file.First<H5Dataset>("dset1");
    // do something with the dataset... read the data into an array:
    Array<double> A = dset.Get<double>(); 
    // ... 
}

using (var file = new H5File("example.h5")) {
    var children = file.First<H5Group>("group1").Find<H5Object>(recursive: false);
    // ... 
}

using (var file = new H5File("example.h5")) {
    foreach (var ds in file.Find<H5Dataset>("set")) {
        // do something with the dataset ds ... read the data into an array:
        Array<double> A = ds.Get<double>(); 
        // ... 
    }
}

using (var file = new H5File("example.h5")) {
    // H5Object is the base type of all common HDF5 objects in ILNumerics
    foreach (var obj in file.Find<H5Object>()) { 
        // write the absolute path of the object
        Console.WriteLine(obj.Path);  
    }
}

Reference