在.NET Core 2.1项目中,我在SQL Server数据库上使用EF Core with Command模式(使用MediatR库)。
我通过使用以下设置来设置项目以避免客户端查询评估:
var phaseOptions = new DbContextOptionsBuilder<PhaseDbContext>().UseSqlServer(configuration.GetConnectionString("PhaseDbContext"),
sqlServerOptions => sqlServerOptions
.EnableRetryOnFailure(
maxRetryCount: 5,
maxRetryDelay: TimeSpan.FromSeconds(30),
errorNumbersToAdd: null))
.ConfigureWarnings(warnings => warnings
.Throw(RelationalEventId.QueryClientEvaluationWarning)) // Disable Client query evaluation
.Options;
现在我用这个查询得到一个QueryClientEvaluationException
:
var articleCodes = await PhaseContext.PhaseArticles
.Where(a => !request.ArticleFamily.HasValue || a.GetArticleFamily() == request.ArticleFamily.Value)
.ToListAsync(cancellationToken);
问题出在a.GetArticleFamily()
方法调用上,因为该方法现在定义如下,在PhaseArticle
实体类中:
public class PhaseArticle
{
public int Id { get; set; }
public string Code { get; set; }
public string Description { get; set; }
public string UnitOfMeasure { get; set; }
public string Category { get; set; }
public string Group { get; set; }
public string Family { get; set; }
public double UnitCost { get; set; }
public string AdditionalDescription { get; set; }
public string ExternalCode { get; set;}
public string ColorCode { get; set;}
public string Note { get; set; }
public ArticleFamily GetArticleFamily()
{
switch (Family)
{
case "CEL":
return ArticleFamily.Cell;
case "STR":
return ArticleFamily.String;
case "RAW":
return ArticleFamily.OtherRawMaterial;
case "SFP":
return ArticleFamily.SemiFinishedPanel;
case "FP":
return ArticleFamily.FinishedPanel;
default:
return ArticleFamily.Other;
}
}
}
现在,我想知道是否有可能通过某种方式重构(并且可能远离实体类)GetArticleFamily()方法来保持QueryClientEvaluationWarning
选项。
@StriplingWarrior我再次更新了有关ValueConverter()
的建议的代码,但现在它给出了这个错误:
无法将Lambda表达式转换为表达式树。
在@StriplingWarrior建议之后,我正在尝试编写自定义转换器,但我无法编译代码。
下面的代码的错误是关于第一个switch
块的返回值(它的string
,但它预计是enum
)和关于第二个开关块的预期输入值(它是string
但它预计是enum
)。
这是代码:
public static void ApplyPhaseConversions<T>(this ModelBuilder modelBuilder)
{
modelBuilder
.Entity<PhaseArticle>()
.Property(e => e.Family)
.HasConversion(new ValueConverter<ArticleFamily, string> {
v =>
{
switch (v)
{
case ArticleFamily.Cell:
return "CEL";
case ArticleFamily.String:
return "STR";
case ArticleFamily.OtherRawMaterial:
return "RAW";
case ArticleFamily.SemiFinishedPanel:
return "SFP";
case ArticleFamily.FinishedPanel:
return "FP";
default:
return "";
}
},
v =>
{
switch (v)
{
case "CEL":
return ArticleFamily.Cell;
case "STR":
return ArticleFamily.String;
case "RAW":
return ArticleFamily.OtherRawMaterial;
case "SFP":
return ArticleFamily.SemiFinishedPanel;
case "FP":
return ArticleFamily.FinishedPanel;
default:
return ArticleFamily.Other;
}
}});
}
看起来你正在使用GetArticleFamily()
在数据库值和C#枚举之间进行转换。 EF Core有一个名为Value Conversions的内置功能,旨在解决这个问题:https://docs.microsoft.com/en-us/ef/core/modeling/value-conversions
您应该能够定义一个ValueConverter来转换为ArticleFamily
值,然后将Family
属性的类型更改为ArticleFamily
,并在查询中使用该属性:
var articleCodes = await PhaseContext.PhaseArticles
.Where(a => !request.ArticleFamily.HasValue || a.Family == request.ArticleFamily.Value)
.ToListAsync(cancellationToken);
PS - 我不确定上面的代码会产生什么样的查询,但是最好像这样编写你的查询:
var articleQuery = PhaseContext.PhaseArticles.AsQueryable();
if(request.ArticleFamily.HasValue)
{
articleQuery = articleQuery.Where(a => a.Family == request.ArticleFamily.Value);
}
var articleCodes = await articleQuery.ToListAsync(cancellationToken);
您可以创建一个新变量并传输request.ArticleFamily.Value结果,以便它可以返回ArticleFamily.Cell或ArticleFamily.String,然后运行查询
EG
if(request != null && !request.ArticleFamily.HasValue)
// or throw an exception here
return ...;
ArticleFamily newVariable = (ArticleFamily)Enum.Parse(typeof(ArticleFamily), request.ArticleFamily);
var articleCodes = await PhaseContext.PhaseArticles
.Where(a => a.Family == newVariable)
.ToListAsync(cancellationToken);
应在运行查询之前完成方法参数的验证。另一件事是如果请求是null
会发生什么?
编辑
还需要验证request
对象。可能存在这样的情况:您在发送到API的JSON对象的结构中输入错误或错误(您在定义字段值后忘记添加逗号)。在这种情况下,请求对象将具有null
值,因此需要验证此类行为。例如。你可以加
if (!ModelState.IsValid)
{
return BadRequest(ModelState);
}
在您的控制器的操作中,以验证整个请求正文。客户端将收到正确的错误消息。
最后,解决方案几乎就在那里,同时@StriplingWarrior说道。
由于C#编译器的限制,无法为此代码创建表达式树,解决方案是将转换代码生成方法,然后在HasConversion
中调用它们。
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder
.Entity<PhaseArticle>()
.Property(e => e.Family)
.HasConversion(new ValueConverter<ArticleFamily, string>(
v => StringFromArticleFamily(v),
v => ArticleFamilyFromString(v));
}
private static ArticleFamily ArticleFamilyFromString(string family)
{
switch (family)
{
case "CEL":
return ArticleFamily.Cell;
case "STR":
return ArticleFamily.String;
case "RAW":
return ArticleFamily.OtherRawMaterial;
case "SFP":
return ArticleFamily.SemiFinishedPanel;
case "FP":
return ArticleFamily.FinishedPanel;
default:
return ArticleFamily.Other;
}
}
private static string StringFromArticleFamily(ArticleFamily articleFamily)
{
switch (articleFamily)
{
case ArticleFamily.Cell:
return "CEL";
case ArticleFamily.String:
return "STR";
case ArticleFamily.OtherRawMaterial:
return "RAW";
case ArticleFamily.SemiFinishedPanel:
return "SFP";
case ArticleFamily.FinishedPanel:
return "FP";
default:
return "";
}
}