Firebase. Database. Query
The Query class (and its subclass, DatabaseReference ) are used for reading data.
Summary
Listeners are attached, and they will be triggered when the corresponding data changes.
Instances of Query are obtained by calling StartAt(), EndAt(), or Limit() on a DatabaseReference.
Inheritance
Direct Known Subclasses:Firebase.Database.DatabaseReference
Properties |
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ChildAdded
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EventHandler< ChildChangedEventArgs >
Event raised when children nodes are added relative to this location.
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ChildChanged
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EventHandler< ChildChangedEventArgs >
Event raised when children nodes are changed relative to this location.
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ChildMoved
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EventHandler< ChildChangedEventArgs >
Event raised when children nodes are moved relative to this location.
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ChildRemoved
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EventHandler< ChildChangedEventArgs >
Event raised when children nodes are removed relative to this location.
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Reference
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A DatabaseReference to this location
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ValueChanged
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EventHandler< ValueChangedEventArgs >
Event for changes in the data at this location.
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Public functions |
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EndAt(string value)
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Create a query constrained to only return child nodes with a value less than or equal to the given value, using the given orderBy directive or priority as default.
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EndAt(double value)
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Create a query constrained to only return child nodes with a value less than or equal to the given value, using the given orderBy directive or priority as default.
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EndAt(bool value)
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Create a query constrained to only return child nodes with a value less than or equal to the given value, using the given orderBy directive or priority as default.
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EndAt(string value, string key)
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Create a query constrained to only return child nodes with a value less than or equal to the given value, using the given orderBy directive or priority as default, and additionally only child nodes with a key key less than or equal to the given key.
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EndAt(double value, string key)
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Create a query constrained to only return child nodes with a value less than or equal to the given value, using the given orderBy directive or priority as default, and additionally only child nodes with a key less than or equal to the given key.
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EndAt(bool value, string key)
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Create a query constrained to only return child nodes with a value less than or equal to the given value, using the given orderBy directive or priority as default, and additionally only child nodes with a key less than or equal to the given key.
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EqualTo(string value)
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Create a query constrained to only return child nodes with the given value
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EqualTo(double value)
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Create a query constrained to only return child nodes with the given value
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EqualTo(bool value)
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Create a query constrained to only return child nodes with the given value.
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EqualTo(string value, string key)
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Create a query constrained to only return the child node with the given key and value.
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EqualTo(double value, string key)
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Create a query constrained to only return the child node with the given key and value.
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EqualTo(bool value, string key)
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Create a query constrained to only return the child node with the given key and value.
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GetValueAsync()
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Task< DataSnapshot >
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KeepSynced(bool keepSynced)
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void
By calling
keepSynced(true) on a location, the data for that location will automatically be downloaded and kept in sync, even when no listeners are attached for that location. |
LimitToFirst(int limit)
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Create a query with limit and anchor it to the start of the window
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LimitToLast(int limit)
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Create a query with limit and anchor it to the end of the window
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OrderByChild(string path)
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Create a query in which child nodes are ordered by the values of the specified path.
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OrderByKey()
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Create a query in which child nodes are ordered by their keys.
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OrderByPriority()
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Create a query in which child nodes are ordered by their priorities.
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OrderByValue()
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Create a query in which nodes are ordered by their value
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StartAt(string value)
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Create a query constrained to only return child nodes with a value greater than or equal to the given value, using the given orderBy directive or priority as default.
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StartAt(double value)
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Create a query constrained to only return child nodes with a value greater than or equal to the given value, using the given orderBy directive or priority as default.
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StartAt(bool value)
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Create a query constrained to only return child nodes with a value greater than or equal to the given value, using the given orderBy directive or priority as default.
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StartAt(string value, string key)
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Create a query constrained to only return child nodes with a value greater than or equal to the given value, using the given orderBy directive or priority as default, and additionally only child nodes with a key greater than or equal to the given key.
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StartAt(double value, string key)
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Create a query constrained to only return child nodes with a value greater than or equal to the given value, using the given orderBy directive or priority as default, and additionally only child nodes with a key greater than or equal to the given key.
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StartAt(bool value, string key)
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Create a query constrained to only return child nodes with a value greater than or equal to the given value, using the given orderBy directive or priority as default, and additionally only child nodes with a key greater than or equal to the given key.
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Properties
ChildAdded
EventHandler< ChildChangedEventArgs > ChildAdded
Event raised when children nodes are added relative to this location.
Register a handler to observe when children are added relative to this Query object. Each time time children nodes are added, your handler will be called with an immutable snapshot of the data.
ChildChanged
EventHandler< ChildChangedEventArgs > ChildChanged
Event raised when children nodes are changed relative to this location.
Register a handler to observe changes to children relative to this Query object. Each time time children nodes are changed, your handler will be called with an immutable snapshot of the data.
ChildMoved
EventHandler< ChildChangedEventArgs > ChildMoved
Event raised when children nodes are moved relative to this location.
Register a handler to observe when children are moved relative to this Query object. Each time time children nodes are moved, your handler will be called with an immutable snapshot of the data.
ChildRemoved
EventHandler< ChildChangedEventArgs > ChildRemoved
Event raised when children nodes are removed relative to this location.
Register a handler to observe when children are removed relative to this Query object. Each time time children nodes are removed, your handler will be called with an immutable snapshot of the data.
ValueChanged
EventHandler< ValueChangedEventArgs > ValueChanged
Event for changes in the data at this location.
Register a handler to observe changes at the location of this Query object. Each time time the data changes, your handler will be called with an immutable snapshot of the data.
Public functions
EndAt
Query EndAt( string value )
Create a query constrained to only return child nodes with a value less than or equal to the given value, using the given orderBy directive or priority as default.
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Parameters |
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Returns |
A Query with the new constraint
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EndAt
Query EndAt( double value )
Create a query constrained to only return child nodes with a value less than or equal to the given value, using the given orderBy directive or priority as default.
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Parameters |
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Returns |
A Query with the new constraint
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EndAt
Query EndAt( bool value )
Create a query constrained to only return child nodes with a value less than or equal to the given value, using the given orderBy directive or priority as default.
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Parameters |
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Returns |
A Query with the new constraint
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EndAt
Query EndAt( string value, string key )
Create a query constrained to only return child nodes with a value less than or equal to the given value, using the given orderBy directive or priority as default, and additionally only child nodes with a key key less than or equal to the given key.
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Returns |
A Query with the new constraint
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EndAt
Query EndAt( double value, string key )
Create a query constrained to only return child nodes with a value less than or equal to the given value, using the given orderBy directive or priority as default, and additionally only child nodes with a key less than or equal to the given key.
Details | |||||
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Parameters |
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Returns |
A Query with the new constraint
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EndAt
Query EndAt( bool value, string key )
Create a query constrained to only return child nodes with a value less than or equal to the given value, using the given orderBy directive or priority as default, and additionally only child nodes with a key less than or equal to the given key.
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Parameters |
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Returns |
A Query with the new constraint
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EqualTo
Query EqualTo( string value )
Create a query constrained to only return child nodes with the given value
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Parameters |
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Returns |
A query with the new constraint
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EqualTo
Query EqualTo( double value )
Create a query constrained to only return child nodes with the given value
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Parameters |
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Returns |
A query with the new constraint
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EqualTo
Query EqualTo( bool value )
Create a query constrained to only return child nodes with the given value.
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Parameters |
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Returns |
A query with the new constraint
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EqualTo
Query EqualTo( string value, string key )
Create a query constrained to only return the child node with the given key and value.
Create a query constrained to only return the child node with the given key and value. Note that there is at most one such child as names are unique.
Known issue This currently does not work properly on iOS and tvOS. Please use EqualTo(string value) instead.
Details | |||||
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Parameters |
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Returns |
A query with the new constraint
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EqualTo
Query EqualTo( double value, string key )
Create a query constrained to only return the child node with the given key and value.
Create a query constrained to only return the child node with the given key and value. Note that there is at most one such child as keys are unique.
Known issue This currently does not work properly on iOS and tvOS. Please use EqualTo(double value) instead.
Details | |||||
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Parameters |
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Returns |
A query with the new constraint
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EqualTo
Query EqualTo( bool value, string key )
Create a query constrained to only return the child node with the given key and value.
Create a query constrained to only return the child node with the given key and value. Note that there is at most one such child as keys are unique.
Known issue This currently does not work properly on iOS and tvOS. Please use EqualTo(bool value) instead.
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Parameters |
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Returns |
A query with the new constraint
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GetValueAsync
Task< DataSnapshot > GetValueAsync()
KeepSynced
void KeepSynced( bool keepSynced )
By calling keepSynced(true)
on a location, the data for that location will automatically be downloaded and kept in sync, even when no listeners are attached for that location.
By calling keepSynced(true)
on a location, the data for that location will automatically be downloaded and kept in sync, even when no listeners are attached for that location.
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Parameters |
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LimitToFirst
Query LimitToFirst( int limit )
Create a query with limit and anchor it to the start of the window
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Returns |
A Query with the new constraint
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LimitToLast
Query LimitToLast( int limit )
Create a query with limit and anchor it to the end of the window
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Parameters |
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Returns |
A Query with the new constraint
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OrderByChild
Query OrderByChild( string path )
Create a query in which child nodes are ordered by the values of the specified path.
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Parameters |
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Returns |
A Query with the new constraint
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OrderByKey
Query OrderByKey()
Create a query in which child nodes are ordered by their keys.
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Returns |
A Query with the new constraint
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OrderByPriority
Query OrderByPriority()
Create a query in which child nodes are ordered by their priorities.
Details | |
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Returns |
A Query with the new constraint
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OrderByValue
Query OrderByValue()
Create a query in which nodes are ordered by their value
Details | |
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Returns |
A Query with the new constraint
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StartAt
Query StartAt( string value )
Create a query constrained to only return child nodes with a value greater than or equal to the given value, using the given orderBy directive or priority as default.
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Parameters |
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Returns |
A Query with the new constraint
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StartAt
Query StartAt( double value )
Create a query constrained to only return child nodes with a value greater than or equal to the given value, using the given orderBy directive or priority as default.
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Parameters |
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Returns |
A Query with the new constraint
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StartAt
Query StartAt( bool value )
Create a query constrained to only return child nodes with a value greater than or equal to the given value, using the given orderBy directive or priority as default.
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Parameters |
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Returns |
A Query with the new constraint
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StartAt
Query StartAt( string value, string key )
Create a query constrained to only return child nodes with a value greater than or equal to the given value, using the given orderBy directive or priority as default, and additionally only child nodes with a key greater than or equal to the given key.
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Parameters |
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Returns |
A Query with the new constraint
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StartAt
Query StartAt( double value, string key )
Create a query constrained to only return child nodes with a value greater than or equal to the given value, using the given orderBy directive or priority as default, and additionally only child nodes with a key greater than or equal to the given key.
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Parameters |
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Returns |
A Query with the new constraint
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StartAt
Query StartAt( bool value, string key )
Create a query constrained to only return child nodes with a value greater than or equal to the given value, using the given orderBy directive or priority as default, and additionally only child nodes with a key greater than or equal to the given key.
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Returns |
A Query with the new constraint
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