ElementId

Description:
The ElementId object is used as a unique identification for an element within a single project.

Remarks:
The Value within the ElementId is only unique with a single project. It is not unique across several projects. The Id can be used to retrieve a specific element from the database when needed. However ids are subject to change during an Autodesk Revit session and as such should not be retained and used across repeated calls to external commands. If a manner is needed to uniquely identify an element beyond this limitation then a shared parameter should be added to the element containing a unique identifier managed by the external application.

Inheritance Hierarchy:
System.Object
Autodesk.Revit.DB.ElementId

public class ElementId : IComparable

Public Class ElementId
	Implements IComparable

public ref class ElementId : IComparable

type ElementId = 
    class
        interface IComparable
    end

Name	Return Type	Description
C ElementId(BuiltInCategory)	None	Create an ElementId handle with the given BuiltInCategory id.
C ElementId(BuiltInParameter)	None	Create an ElementId handle with the given BuiltInParameter id.
C ElementId(Int64)	None	Create an ElementId handle with the given 64-bit integer id.

Name	Return Type	Description	Inherited From
M Compare(ElementId)	Int32	Compares two element ids.
M CompareTo(Object)	Int32	Compares two element ids. Implementation of System.IComparable interface
M Equals(Object)	Boolean	Determines whether the specified Object is equal to the current Object . (Overrides Object . Equals(Object) )
M GetHashCode()	Int32	Gets the value of the id as hash code (Overrides Object . GetHashCode () )
M GetType	None	Gets the Type of the current instance. (Inherited from Object )	Object
M Parse(String)	ElementId	Parse the string representation of the id into a corresponding ElementId.
M ToString()	String	Gets a String representation of the value of the id. (Overrides Object . ToString () )
M TryParse(String, ElementId%)	Boolean	Parse the string representation of the id into a corresponding ElementId.

Name	Return Type	Description
O Equality(ElementId, ElementId)	Boolean	Determines whether these two ElementIds are the same.
O GreaterThan(ElementId, ElementId)	Boolean	Determines whether one element id is greater than another element id.
O GreaterThanOrEqual(ElementId, ElementId)	Boolean	Determines whether one element id is not less than another element id.
O Inequality(ElementId, ElementId)	Boolean	Determines whether these two ElementIds are different.
O LessThan(ElementId, ElementId)	Boolean	Determines whether this element id is less than another element id.
O LessThanOrEqual(ElementId, ElementId)	Boolean	Determines whether one element id is not greater than another element id.

Name	Return Type	Description	Inherited From
P InvalidElementId	ElementId	Get the invalid ElementId whose value is -1.
P Value	long	Provides the value of the element id as a 64-bit integer.