[英]How can I make my class act like a Guid when used in Linq?
我將Cosmosdb與.net CORE 2.2和Cosmosdb SQL SDK結合使用。 默認情況下,cosmosdb將為每個文檔分配“ Id”屬性作為Guid。 但是僅憑ID不足以直接讀取文檔,還必須知道其分區。 因此,我創建了一個名為CosmosGuid的類,其中包含一個Id屬性(Guid)和一個PartitionKey屬性(字符串)。 ToString()被重寫以在Guid上調用.ToString(“ N”)來刪除破折號,並將PartitionKey附加到末尾。 我遇到的問題是,當我在Linq中使用CosmosGuid時,生成的SQL將包含CosmosGuid的json版本,我真的需要它只是一個字符串。 我可以調用.ToString(),這將產生所需的結果,但是恐怕其他開發人員會在Linq表達式中使用我的類,並且由於未知原因它會失敗。 當我保存CosmosGuid時,我創建了一個自定義的newtonsoft轉換器,以在保存時調用ToString()並在讀取時調用.Parse(string)。 當您在Linq中比較兩個Guid時,生成的SQL出現在一個字符串中,但是當我比較兩個CosmosGuid時,它會創建我的類的json字符串。 我怎樣才能使我的班級表現得像個向導?
我已經嘗試實現與Guid相同的所有接口。 我來的關閉是實現“ IEnumerable”,並在GetComparer()中返回:
new string[] { this.ToString() }.GetEnumerator();
產生的代碼是完美的,但是它始終使我的字符串被方括號[]包圍。
這是一個例子:
SELECT VALUE root FROM root WHERE (root['id'] = ['9a9dbbd5f78143c48b16f780c7ceaa4011'])
這是CosmosGuid類,我認為id是完整類,因為它不是很大,並且可能對某些有用。
public class CosmosGuid
{
// This is the unique Id of the entity
public Guid Guid { get; set; }
// This is the partition key where the entity lives
public string PartitionKey { get; set; }
// This is the unique Id of the Document that contains the entity
public Guid? ParentGuid { get; set; }
// This is the PartitionKey of the Document that contains the entity
public string ParentPartitionKey { get; set; }
/// <summary>
/// Parses a CosmosGuid string into a new CosmosGuid
/// </summary>
/// <param name="cosmosGuid"></param>
public CosmosGuid(string cosmosGuid)
{
ParentGuid = null;
ParentPartitionKey = null;
try
{
var parsed = cosmosGuid.Split('-');
// We can accuratly parse the guid from the string by always grabing the first 32 characters.
// The characters after the first 32 are the PartitionKey.
// https://stackoverflow.com/a/4458925
// Guid.NewGuid().ToString("N") => 32 characters (digits only, no dashes)
Guid = Guid.Parse(parsed[0].Substring(0, 32));
PartitionKey = parsed[0].Substring(32, parsed[0].Length - 32);
if (parsed.Length == 2)
{
ParentGuid = Guid.Parse(parsed[1].Substring(0, 32));
ParentPartitionKey = parsed[1].Substring(32, parsed[1].Length - 32);
}
}
catch (Exception ex)
{
throw new Exception("The Id of the document is not a properly formatted CosmosGuid.", ex);
}
}
/// <summary>
/// Generates a new Guid and appends the PartitionKey. This is used for Documents.
/// </summary>
/// <param name="partitionKey"></param>
/// <returns></returns>
public static CosmosGuid NewCosmosGuid(string partitionKey)
{
return new CosmosGuid($"{ShortenGuid(Guid.NewGuid())}{partitionKey}");
}
/// <summary>
/// Generates a new Guid and appends the PartitionKey as well as the Parent Guid and Parent PartitionKey. This is used for Subdocuments.
/// </summary>
/// <param name="parent"></param>
/// <param name="partitionKey"></param>
/// <returns></returns>
public static CosmosGuid NewCosmosGuid(CosmosGuid parent, string partitionKey)
{
return new CosmosGuid($"{ShortenGuid(Guid.NewGuid())}{partitionKey}-{ShortenGuid(parent.Guid)}{parent.PartitionKey}");
}
/// <summary>
/// Returns only the Parent CosmosGuid. If there is no parent the value returned will be null.
/// </summary>
public CosmosGuid Parent
{
get
{
if (ParentGuid != null && ParentPartitionKey != null)
return new CosmosGuid($"{ShortenGuid((Guid)ParentGuid)}{ParentPartitionKey}");
else
return null;
}
}
/// <summary>
/// Parses a CosmosGuid string into a new CosmosGuid.
/// </summary>
/// <param name="cosmosGuid"></param>
/// <returns></returns>
public static CosmosGuid Parse(string cosmosGuid)
{
return new CosmosGuid(cosmosGuid);
}
/// <summary>
/// Generates a CosmosGuid formatted string.
/// </summary>
/// <returns></returns>
public override string ToString()
{
if (ParentGuid == null)
return $"{ShortenGuid(Guid)}{PartitionKey}";
else
return $"{ShortenGuid(Guid)}{PartitionKey}-{ShortenGuid((Guid)ParentGuid)}{ParentPartitionKey}";
}
/// <summary>
/// Removes the dashes from a Guid
/// </summary>
/// <param name="guid"></param>
/// <returns></returns>
private static string ShortenGuid(Guid guid)
{
// Just remove dashes from the guid to shorten it some.
// More can be done here if you wish but make sure the guid uniqueness isnt compromised.
return guid.ToString("N");
}
public static bool operator ==(CosmosGuid obj1, CosmosGuid obj2)
{
return obj1?.ToString() == obj2?.ToString();
}
public static bool operator !=(CosmosGuid obj1, CosmosGuid obj2)
{
return obj1?.ToString() != obj2?.ToString();
}
}
如果開發人員喜歡在哪里使用CosmosGuid,它將無法工作,因為生成的SQL是該類的Json版本。 (該ID也是CosmosGuid):
var cosmosGuid = CosmosGuid.Parse("6bec688a0aca477c8175c09162b7a9b411");
var result = await Client.CreateDocumentQuery<MyClass>(UriFactory.CreateDocumentCollectionUri(DatabaseId, CollectionId), options)
.Where(x => x.Id == cosmosGuid)
.AsDocumentQuery();
這是生成的sql
SELECT VALUE root FROM root WHERE (root['id'] = {'Guid':'6bec688a-0aca-477c-8175-c09162b7a9b4','PartitionKey':'11','ParentGuid':null,'ParentPartitionKey':null,'Parent':null})
而是,開發人員必須在代碼中的任何地方調用.ToString()。
var cosmosGuid = CosmosGuid.Parse("6bec688a0aca477c8175c09162b7a9b411");
var result = await Client.CreateDocumentQuery<MyClass>(UriFactory.CreateDocumentCollectionUri(DatabaseId, CollectionId), options)
.Where(x => x.Id.ToString() == cosmosGuid.ToString())
.AsDocumentQuery();
這是生成的Sql
SELECT VALUE root FROM root WHERE (root['id'] = '6bec688a0aca477c8175c09162b7a9b411')
如果刪除CosmosGuid並恢復為僅使用Guid作為Id屬性,則Cosmosdb SDK生成的SQL可以正常工作。 在Linq中使用時,如何使我的班級像.net Guid一樣工作?
對於LINQ to對象:
您可以在CosmosGuid
類上重載==
運算符,請參見operator keyword 。
另外,您可以實現IEquatable<Guid>
並改用.Equals()
:
public class CosmosGuid : IEquatable<Guid>
{
....
public bool Equals(Guid other) {
return this.Guid == other;
}
}
.Where(x => cosmosGuid.Equals(x.Id))
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