Dictionary<'TKey, 'TValue> Constructor (IDictionary<'TKey, 'TValue>, IEqualityComparer<'TKey>)
Initializes a new instance of the Dictionary<'TKey, 'TValue> class that contains elements copied from the specified IDictionary<'TKey, 'TValue> and uses the specified IEqualityComparer<'T>.
Assembly: mscorlib (in mscorlib.dll)
new :
dictionary:IDictionary<'TKey, 'TValue> *
comparer:IEqualityComparer<'TKey> -> Dictionary
Parameters
- dictionary
-
Type:
System.Collections.Generic.IDictionary<'TKey, 'TValue>
The IDictionary<'TKey, 'TValue> whose elements are copied to the new Dictionary<'TKey, 'TValue>.
- comparer
-
Type:
System.Collections.Generic.IEqualityComparer<'TKey>
The IEqualityComparer<'T> implementation to use when comparing keys, or null to use the default EqualityComparer<'T> for the type of the key.
| Exception | Condition |
|---|---|
| ArgumentNullException | dictionary is null. |
| ArgumentException | dictionary contains one or more duplicate keys. |
Use this constructor with the case-insensitive string comparers provided by the StringComparer class to create dictionaries with case-insensitive string keys.
Every key in a Dictionary<'TKey, 'TValue> must be unique according to the specified comparer; likewise, every key in the source dictionary must also be unique according to the specified comparer.
Note |
|---|
For example, duplicate keys can occur if comparer is one of the case-insensitive string comparers provided by the StringComparer class and dictionary does not use a case-insensitive comparer key. |
The initial capacity of the new Dictionary<'TKey, 'TValue> is large enough to contain all the elements in dictionary.
Dictionary<'TKey, 'TValue> requires an equality implementation to determine whether keys are equal. If comparer is null, this constructor uses the default generic equality comparer, EqualityComparer<'T>.Default. If type TKey implements the System.IEquatable<'T> generic interface, the default equality comparer uses that implementation.
This constructor is an O(n) operation, where n is the number of elements in dictionary.
The following code example shows how to use the Dictionary<'TKey, 'TValue>(IDictionary<'TKey, 'TValue>, IEqualityComparer<'TKey>) constructor to initialize a Dictionary<'TKey, 'TValue> with case-insensitive sorted content from another dictionary. The code example creates a SortedDictionary<'TKey, 'TValue> with a case-insensitive comparer and populates it with data in random order, then passes the SortedDictionary<'TKey, 'TValue> to the Dictionary<'TKey, 'TValue>(IDictionary<'TKey, 'TValue>, IEqualityComparer<'TKey>) constructor, along with a case-insensitive equality comparer, creating a Dictionary<'TKey, 'TValue> that is sorted. This is useful if you need to build a sorted dictionary that at some point becomes static; copying the data from a SortedDictionary<'TKey, 'TValue> to a Dictionary<'TKey, 'TValue> improves retrieval speed.
Note |
|---|
When you create a new dictionary with a case-insensitive comparer and populate it with entries from a dictionary that uses a case-sensitive comparer, as in this example, an exception occurs if the input dictionary has keys that differ only by case. |
Available since 8
.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
