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| 1 | +# Castle DictionaryAdapter - Customizing Adapter Keys |
| 2 | + |
| 3 | +By default DictionaryAdapter will use very simple strategy when inserting/retrieving data to/from dictionary via adapter - property name becomes the key. |
| 4 | + |
| 5 | +So doing: |
| 6 | + |
| 7 | +``` |
| 8 | +adapter.Name = "Stefan"; |
| 9 | +``` |
| 10 | + |
| 11 | +is identical to doing |
| 12 | + |
| 13 | +```csharp |
| 14 | +dictionary["Name"] = "Stefan"; |
| 15 | +``` |
| 16 | + |
| 17 | +Same with reading |
| 18 | + |
| 19 | +```csharp |
| 20 | +var name = adapter.Name; |
| 21 | +``` |
| 22 | + |
| 23 | +is identical to doing |
| 24 | + |
| 25 | +```csharp |
| 26 | +var name = (string)dictionary["Name"]; |
| 27 | +``` |
| 28 | + |
| 29 | +:information_source: **A word about conversion:** Well that's not entirely true. DictionaryAdapter uses a more sophisticated mechanism for conversion than just plain casting. |
| 30 | + |
| 31 | +This is a fine default, but the adapter lets you customize that behavior using attributes. |
| 32 | + |
| 33 | +For the examples below, lets assume the setup is as follows: |
| 34 | + |
| 35 | +```csharp |
| 36 | +var dictionary = new Hashtable(); |
| 37 | +var adapter = new DictionaryAdapterFactory.GetAdapter<IPerson>(dictionary); |
| 38 | +``` |
| 39 | + |
| 40 | +## Standard Attributes |
| 41 | + |
| 42 | +Out of the box DictionaryAdapter provides set of attributes that should suffice for majority of cases. |
| 43 | + |
| 44 | +### `Key` Attribute |
| 45 | + |
| 46 | +If you want the property name and dictionary key to be totally unrelated you can override the default name using `KeyAttribute`. |
| 47 | + |
| 48 | +```csharp |
| 49 | +public interface IPerson |
| 50 | +{ |
| 51 | + [Key("PersonId")] |
| 52 | + string Name {get; set;} |
| 53 | +} |
| 54 | +``` |
| 55 | + |
| 56 | +Now: |
| 57 | + |
| 58 | +```csharp |
| 59 | +adapter.Name == dictionary["PersonId"]; |
| 60 | +``` |
| 61 | + |
| 62 | +### `KeyPrefix` Attribute |
| 63 | + |
| 64 | +If you would like to prefix all keys in dictionary with some string use `KeyPrefixAttribute`. |
| 65 | + |
| 66 | +```csharp |
| 67 | +[KeyPrefix("Person")] |
| 68 | +public interface IPerson |
| 69 | +{ |
| 70 | + string Name {get; set;} |
| 71 | +} |
| 72 | +``` |
| 73 | + |
| 74 | +Now: |
| 75 | + |
| 76 | +```csharp |
| 77 | +adapter.Name == dictionary["PersonName"]; |
| 78 | +``` |
| 79 | + |
| 80 | +If we had more properties on the interface, they'd all get prefixed. |
| 81 | + |
| 82 | +### `TypeKeyPrefix` Attribute |
| 83 | + |
| 84 | +If you would like to prefix all keys in dictionary with full name of the interface use `TypeKeyPrefixAttribute`. This is especially useful when you have multiple adapters over common dictionary and you want to avoid one overriding another. |
| 85 | + |
| 86 | +```csharp |
| 87 | +[TypeKeyPrefix] |
| 88 | +public interface IPerson |
| 89 | +{ |
| 90 | + string Name {get; set;} |
| 91 | +} |
| 92 | +``` |
| 93 | + |
| 94 | +Now: |
| 95 | + |
| 96 | +```csharp |
| 97 | +adapter.Name == dictionary["Acme.Crm.IPerson#Name"]; |
| 98 | +``` |
| 99 | + |
| 100 | +If we had more properties on the interface, they'd all get prefixed. |
| 101 | + |
| 102 | +### `KeySubstitution` Attribute |
| 103 | + |
| 104 | +If you would like to replace certain characters in your key use `TypeKeyPrefixAttribute`. This is especially useful when you want to use certain characters in your key, that are not legal in C# names. You can set the attribute at interface level, or at property level. |
| 105 | + |
| 106 | +```csharp |
| 107 | +public interface IPerson |
| 108 | +{ |
| 109 | + [KeySubstitution("_",".")] |
| 110 | + string Full_Name {get; set;} |
| 111 | +} |
| 112 | +``` |
| 113 | + |
| 114 | +Now: |
| 115 | + |
| 116 | +```cs`harp |
| 117 | +adapter.Full_Name == dictionary["Full.Name"]; |
| 118 | +``` |
| 119 | +
|
| 120 | +## Creating Custom Attributes |
| 121 | +
|
| 122 | +Custom attributes need to implement two interfaces: |
| 123 | +
|
| 124 | +* `IDictionaryBehavior` - Standard base type for all DictionaryAdapter attributes. Usually you'll inherit base `DictionaryBehaviorAttribute` class and forget about it. |
| 125 | +* `IDictionaryKeyBuilder` - that's the contract for customizing the key. |
| 126 | +
|
| 127 | +### Example - `KeyPostfix` Attribute |
| 128 | +
|
| 129 | +As an example let's assume we want to create attribute that adds common postfix to the property keys, so that we can use it like follows: |
| 130 | +
|
| 131 | +```csharp |
| 132 | +public interface IPerson |
| 133 | +{ |
| 134 | + [KeyPostfix("Person")] |
| 135 | + string Name {get; set;} |
| 136 | +} |
| 137 | +``` |
| 138 | + |
| 139 | +and get: |
| 140 | + |
| 141 | +```csharp |
| 142 | +adapter.Name == dictionary["NamePerson"]; |
| 143 | +``` |
| 144 | + |
| 145 | +Simple implementation might look like this: |
| 146 | + |
| 147 | +```csharp |
| 148 | +[AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = true)] |
| 149 | +public class KeyPostfixAttribute : DictionaryBehaviorAttribute, IDictionaryKeyBuilder |
| 150 | +{ |
| 151 | + private String postfix; |
| 152 | + |
| 153 | + public KeyPrefixAttribute(string keyPrefix) |
| 154 | + { |
| 155 | + this.postfix = keyPrefix; |
| 156 | + } |
| 157 | + |
| 158 | + String IDictionaryKeyBuilder.GetKey(IDictionaryAdapter dictionaryAdapter, String key, PropertyDescriptor property) |
| 159 | + { |
| 160 | + return key + postfix; |
| 161 | + } |
| 162 | +} |
| 163 | +``` |
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