Question

为什么我得到一个参数异常，说我将错误数量的参数传递给string.equals方法？

我传递了三个论点，这应该是正确的。实际上它应该抛出编译时错误而不是运行时...

你看到错误吗？

var translations = await (from l in context.Languages
                  join t in context.Translations on l.ISO639_ISO3166 equals t.ISO639_ISO3166
                  where string.Equals(l.ApplicationName, applicationName, StringComparison.InvariantCultureIgnoreCase)
                  select new Translation
                  {
                      Key = t.Key,
                      Text = t.Text
                  }).ToListAsync();

更新

Test Name:  GetTranslations
Test FullName:  TaaS.IntegrationTests.Tests.TranslationRepositoryTests.GetTranslations
Test Source:    C:\test\TaaS-WebApplication\TaaS.IntegrationTests\Tests\TranslationRepositoryTests.cs : line 17
Test Outcome:   Failed
Test Duration:  0:00:00,0473367

Result StackTrace:  
at System.Linq.Expressions.Expression.GetMethodBasedBinaryOperator(ExpressionType binaryType, Expression left, Expression right, MethodInfo method, Boolean liftToNull)
   at System.Linq.Expressions.Expression.Equal(Expression left, Expression right, Boolean liftToNull, MethodInfo method)
   at System.Data.Entity.Core.Objects.ELinq.LinqExpressionNormalizer.VisitMethodCall(MethodCallExpression m)
   at System.Linq.Expressions.EntityExpressionVisitor.Visit(Expression exp)
   at System.Linq.Expressions.EntityExpressionVisitor.VisitLambda(LambdaExpression lambda)
   at System.Linq.Expressions.EntityExpressionVisitor.Visit(Expression exp)
   at System.Linq.Expressions.EntityExpressionVisitor.VisitUnary(UnaryExpression u)
   at System.Linq.Expressions.EntityExpressionVisitor.Visit(Expression exp)
   at System.Linq.Expressions.EntityExpressionVisitor.VisitExpressionList(ReadOnlyCollection`1 original)
   at System.Linq.Expressions.EntityExpressionVisitor.VisitMethodCall(MethodCallExpression m)
   at System.Data.Entity.Core.Objects.ELinq.LinqExpressionNormalizer.VisitMethodCall(MethodCallExpression m)
   at System.Linq.Expressions.EntityExpressionVisitor.Visit(Expression exp)
   at System.Linq.Expressions.EntityExpressionVisitor.VisitExpressionList(ReadOnlyCollection`1 original)
   at System.Linq.Expressions.EntityExpressionVisitor.VisitMethodCall(MethodCallExpression m)
   at System.Data.Entity.Core.Objects.ELinq.LinqExpressionNormalizer.VisitMethodCall(MethodCallExpression m)
   at System.Linq.Expressions.EntityExpressionVisitor.Visit(Expression exp)
   at System.Data.Entity.Core.Objects.ELinq.ExpressionConverter..ctor(Funcletizer funcletizer, Expression expression)
   at System.Data.Entity.Core.Objects.ELinq.ELinqQueryState.CreateExpressionConverter()
   at System.Data.Entity.Core.Objects.ELinq.ELinqQueryState.GetExecutionPlan(Nullable`1 forMergeOption)
   at System.Data.Entity.Core.Objects.ObjectQuery`1.<>c__DisplayClassc.<GetResultsAsync>b__a()
   at System.Data.Entity.Core.Objects.ObjectContext.<ExecuteInTransactionAsync>d__3d`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.<ExecuteAsyncImplementation>d__9`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Data.Entity.Utilities.TaskExtensions.CultureAwaiter`1.GetResult()
   at System.Data.Entity.Core.Objects.ObjectQuery`1.<GetResultsAsync>d__e.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Data.Entity.Utilities.TaskExtensions.CultureAwaiter`1.GetResult()
   at System.Data.Entity.Internal.LazyAsyncEnumerator`1.<FirstMoveNextAsync>d__0.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Data.Entity.Infrastructure.IDbAsyncEnumerableExtensions.<ForEachAsync>d__5`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at TaaS.Repository.TranslationRepository.<GetTranslationsAsync>d__2.MoveNext() in C:\_REPOSITORIES\taas-application\TaaS-WebApplication\TaaS.Repository\TranslationRepository.cs:line 20
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at TaaS.IntegrationTests.Tests.TranslationRepositoryTests.GetTranslations() in C:\_REPOSITORIES\taas-application\TaaS-WebApplication\TaaS.IntegrationTests\Tests\TranslationRepositoryTests.cs:line 45
Result Message: 
Test method TaaS.IntegrationTests.Tests.TranslationRepositoryTests.GetTranslations threw exception: 
System.ArgumentException: Incorrect number of arguments supplied for call to method 'Boolean Equals(System.String, System.String, System.StringComparison)'

Answer 1

首先，SQL字符串比较不区分大小写，或者说，最常见的排序规则不区分大小写。

您根本不需要使用String.Equals。尝试执行查询而不 String.Equals来电。

如果由于某种原因，查询无法返回结果，则参数或数据可能存在问题。您应该尝试直接执行等效的SQL语句，并检查是否任何匹配的结果。

只有当基础列的排序规则被修改为对字符串敏感的排序规则时，字符串大小写才是问题。这将是非常异常。实际上，困难的部分是让LINQ到EF进行case-敏感查询。

至于错误本身，它是由于String.Equals无法转换为SQL而引起的。 LINQ本身不执行查询，它只是一种语言。 LINQ提供程序负责将查询转换为底层语言并执行它们。

某些提供程序（如LINQ to SQL）将解析它们可能的任何内容，将结果加载到内存中并将其传递给LINQ to Object以进行不受支持的操作。这通常会导致非常性能不佳。在您的情况下，您的查询会将所有翻译加载到内存中，然后尝试过滤它们。

另一方面，LINQ to EF不允许这样做以防止出现性能问题。无法执行的查询不会被执行。特别是String.Equals无法转换为SQL，因为字符串比较由特定于文化的排序规则控制。没有相当于Invariant Culture。

如果您的表区分大小写，则必须更改用于比较的排序规则，例如更改为Latin1_CI_AS。这个SO question描述了各种方法

Answer 2

这是一个运行时错误，因为您可能正在运行Linq query provider，它需要从您的C＃代码创建的expression C＃编译器并在运行时执行它。提供者可能无法转换Equals的这种重载。

尝试将Linq查询更改为：

<span>{{getGroupType(groupType)}}</span>

Answer 3

在 Linq 中，您需要使用 equals 的静态方法。改为这样做，它会起作用：

where l.ApplicationName.Equals(applicationName, StringComparison.InvariantCultureIgnoreCase)

为调用方法＆＃39;布尔等于提供的参数数量不正确

3 个答案: