NET 5 is the implementation of. NET that Microsoft is actively developing. It's a single product with a uniform set of capabilities and APIs that can be used for Windows desktop apps and cross-platform console apps, cloud services, and websites. This TFM is for code that runs everywhere. With a few exceptions, it includes only technologies that work cross-platform. NET 5 code, net5. For existing code that targets netstandard , there's no need to change the TFM to net5.
The only reason to retarget from. NET Standard to. For example, in order to use C 9, you need to target. NET 5. You can multitarget. NET Standard to get access to newer features and still have your library available to other.
If you're using libraries to break down an application into several components, we recommend you target net5. NET 5 version that your application can target. For simplicity, it's best to keep all projects that make up your application on the same version of. Then you can assume the same BCL features everywhere. If you're building reusable libraries that you plan to ship on NuGet, consider the trade-off between reach and available feature set.
NET Framework, so it gives good reach with a fairly large feature set. We don't recommend targeting. If you don't need to support. NET Framework, you could go with. We recommend you skip. Most widely used libraries will end up multi-targeting for both. NET 5 ensures you can leverage the latest platform features for customers that are already on. Here are some problems with.
NET Standard that help explain why. NET 5 is the better way to share code across platforms and workloads:. NET implementations would have to support, so there was a review process for proposals to add new APIs. The goal was to standardize only APIs that could be implemented in all current and future.
NET platforms. The result was that if a feature missed a particular release, you might have to wait for a couple of years before it got added to a version of the Standard. Then you'd wait even longer for the new version of. NET Standard to be widely supported. Solution in. NET 5: When a feature is implemented, it's already available for every. Each element name therein is a hyperlink to its own illustration.
References to properties of information items as defined in [XML Infoset] are notated as links to the relevant section thereof, set off with square brackets, for example [children]. Properties which this specification defines for information items are introduced as follows:. References to properties of information items defined in this specification are notated as links to their introduction as exemplified above, set off with square brackets, for example [new property].
The "dot operator" described above for components and their properties is also used for information items and their properties.
For a given information item I , an expression of the form " I. Lists of normative constraints are typically introduced with phrase like "all of the following are true" or " The phrase "one of the following is true" is used in cases where the authors believe the items listed to be mutually exclusive so that the distinction between "exactly one" and "one or more" does not arise.
If the items in such a list are not in fact mutually exclusive, the phrase "one of the following" should be interpreted as meaning "one or more of the following". The phrase "the appropriate case among the following" is used only when the cases are thought by the authors to be mutually exclusive; if the cases in such a list are not in fact mutually exclusive, the first applicable case should be taken.
Once a case has been encountered with a true condition, subsequent cases must not be tested. Within normative prose in this specification, the words may , should , must and must not are defined as follows:.
The specific wording follows that of [XML 1. Where these terms appear without special highlighting, they are used in their ordinary senses and do not express conformance requirements. Where these terms appear highlighted within non-normative material e. An XSD schema is a set of components such as type definitions and element declarations.
These can be used to assess the validity of well-formed element and attribute information items as defined in [XML Infoset] , and furthermore to specify additional information about those items and their descendants. The input information set is also augmented with information about the validity of the item, or about other properties described in this specification.
The mechanisms by which processors provide such access to the PSVI are neither defined nor constrained by this specification. Throughout this specification, [Definition:] the word assessment is used to refer to the overall process of local validation, recursive determination of validation outcome, and infoset augmentation, i. In general, a valid document is a document whose contents obey the constraints expressed in a particular schema. Since a document may be validated against many different schemas, it is often clearer to speak of a document being valid against a particular schema.
This specification builds on [XML 1. The concepts and definitions used herein regarding XML are framed at the abstract level of information items as defined in [XML Infoset]. By definition, this use of the infoset provides a priori guarantees of well-formedness as defined in [XML 1. Just as [XML 1. In defining schemas in terms of an abstract data model, this specification rigorously specifies the information which must be available to a conforming XSD processor.
The abstract model for schemas is conceptual only, and does not mandate any particular implementation or representation of this information. To facilitate interoperation and sharing of schema information, a normative XML interchange format for schemas is provided.
There are several kinds of schema component, falling into three groups. The primary schema components, which may type definitions or must element and attribute declarations have names, are as follows:. Finally, the "helper" schema components provide small parts of other schema components; they are dependent on their context:. The name [Definition:] Component covers all the different kinds of schema component defined in this specification.
On the other hand, [Definition:] definition components define internal schema components that can be used in other schema components. An expanded name , as defined in [XML Namespaces 1. Type definitions form a hierarchy with a single root.
The subsections below first describe characteristics of that hierarchy, then provide an introduction to simple and complex type definitions themselves. In most cases, a type definition is derived from other type definitions. The added constraints might include narrowed ranges or reduced alternatives. The definition of anyType serves as default type definition for element declarations whose XML representation does not specify one.
The XSD error type has no valid instances. It can be used in any place where other types are normally used; in particular, it can be used in conditional type assignment to cause elements which satisfy certain conditions to be invalid.
For brevity, the text and examples in this specification often use the qualified names xs:anyType and xs:error for these type definitions. Informally, it applies to the values of attributes and the text-only content of elements. This type definition is often referred to simply as " xs:anyAtomicType ". It too is considered to have an unconstrained lexical space. Its value space consists of the union of the value spaces of all the primitive datatypes.
It also provides mechanisms for constructing new simple type definitions whose members are lists of items themselves constrained by some other simple type definition, or whose membership is the union of the memberships of some other simple type definitions.
The latter also defines an extensive inventory of pre-defined simple types. A complex type definition is a set of attribute declarations and a content type, applicable to the [attributes] and [children] of an element information item respectively. The content type may require the [children] to contain neither element nor character information items that is, to be empty , or to be a string which belongs to a particular simple type, or to contain a sequence of element information items which conforms to a particular model group, with or without character information items as well.
There are three kinds of declaration component: element, attribute, and notation. Each is described in a section below. Also included is a discussion of element substitution groups, which is a feature provided in conjunction with element declarations. An element declaration is an association of a name with a type definition, either simple or complex, an optional default value and a possibly empty set of identity-constraint definitions.
The association is either global or scoped to a containing complex type definition. A top-level element declaration with name 'A' is broadly comparable to a pair of DTD declarations as follows, where the associated type definition fills in the ellipses:. All such members must have type definitions which are either the same as the head's type definition or derived from it.
Note that element substitution groups are not represented as separate components. An attribute declaration is an association between a name and a simple type definition, together with occurrence information and optionally a default value. The association is either global, or local to its containing complex type definition. A notation declaration is an association between a name and an identifier for a notation. The model group, particle, and wildcard components contribute to the portion of a complex type definition that controls an element information item's content.
A model group is a constraint in the form of a grammar fragment that applies to lists of element information items. It consists of a list of particles, i. There are three varieties of model group:. Each model group denotes a set of sequences of element information items.
Regarding that set of sequences as a language, the set of sequences recognized by a group G may be written L G. A particle is a term in the grammar for element content, consisting of either an element declaration, a wildcard or a model group, together with occurrence constraints.
The name [Definition:] Term is used to refer to any of the three kinds of components which can appear in particles. Each content model, indeed each particle and each term, denotes a set of sequences of element information items. Regarding that set of sequences as a language, the set of sequences recognized by a particle P may be written L P.
Similarly, a term T accepts or recognizes the members of L T. An attribute use plays a role similar to that of a particle, but for attribute declarations: an attribute declaration used by a complex type definition is embedded within an attribute use, which specifies whether the declaration requires or merely allows its attribute, and whether it has a default or fixed value.
A wildcard is a special kind of particle which matches element and attribute information items dependent on their namespace names and optionally on their local names.
This section describes constructs which use [XPath 2. Identity-constraint definitions are associated with element declarations; assertions are associated with type definitions; conditional type assignment using type alternatives allows the type of an element instance to be chosen based on properties of the element instance in particular, based on the values of its attributes. An identity-constraint definition is an association between a name and one of several varieties of identity-constraint related to uniqueness and reference.
All the varieties use [XPath 2. A Type Alternative component type alternative for short associates a type definition with a predicate. An assertion is a predicate associated with a type, which is checked for each instance of the type. Many rules that can be enforced by identity constraints and conditional type assignment can also be formulated in terms of assertions.
That is, the various constructs have overlapping functionality. The three forms of constraint differ from each other in various ways which may affect the schema author's choice of formulation. Less obviously, identity constraints are associated with element declarations, while assertions are associated with type definitions. If it is desired to enforce a particular property of uniqueness or referential integrity associated with a particular element declaration E , of type T , the schema author may often choose either an identity constraint associated with E , or an assertion associated with T.
One obvious difference is that elements substitutable for E are required to have types derived from T , but are not required to enforce the identity constraints or the nillability of E. If the constraint applicable to E should be enforced by elements substitutable for E , it is often most convenient to formulate the constraint as an assertion on T ; conversely, if only some elements of type T are intended to be subject to the constraint, or if elements substitutable for E need not enforce the constraint, then it will be more convenient to formulate the rule as an identity constraint on E.
Similar considerations sometimes apply to the choice between assertions and conditional type assignment. Because identity constraints and conditional type assignment are simpler and less variable than assertions, it may be easier for software to exploit or optimize them.
Assertions have greater expressive power, which means they are often convenient. The "rule of least power" applies here; it is often preferable to use a less expressive notation in preference to a more expressive one, when either will suffice. See [Rule of Least Power]. There are two kinds of convenience definitions provided to enable the re-use of pieces of complex type definitions: model group definitions and attribute group definitions. A model group definition is an association between a name and a model group, enabling re-use of the same model group in several complex type definitions.
An attribute group definition is an association between a name and a set of attribute declarations, enabling re-use of the same set in several complex type definitions. The interpretation of such information is not defined in this specification. The [XML 1. The last of these, schema information set contributions, are not as new as they might at first seem. XML validation augments the XML information set in similar ways, for example by providing values for attributes not present in instances, and by implicitly exploiting type information for normalization or access.
By including schema information set contributions, this specification makes explicit some features that XML leaves implicit. Within the context of this specification, conformance can be claimed for schema documents, for schemas, and for processors.
This specification distinguishes several classes of conforming processors, which are defined in terms of the following concepts. A claim that a processor conforms to this specification must specify to which processor classes defined here the processor belongs. As noted above, in general a document is valid against a particular schema if it obeys the constraints imposed by that schema.
Depending on the nature of the application and on the specific invariants to be enforced, different forms of validity may be appropriately required by an application, a specification, or other users of XSD. This section defines terminology for use in describing the requirements of applications or other technologies which use XSD schema to describe constraints on XML documents.
Therefore [Definition:] this specification introduces the term symbol space to denote a collection of names, each of which is unique with respect to the others. Within a given symbol space, names must be unique; as a consequence, each expanded name within a given symbol space uniquely identifies a single component.
The same expanded name may however appear in more than one symbol space without conflict. For example, assuming that the namespace prefix my is bound to some particular namespace, both a simple type definition and a top-level element declaration can bear the name my:abc without conflict or necessary relation between the two.
But it is not possible for both a simple type definition and a complex type definition, or two distinct top-level element declarations, to share the name my:abc. Locally scoped attribute and element declarations are special with regard to symbol spaces. Their names are not regarded as being in any particular symbol space. So, for example, two complex type definitions having the same target namespace can contain a local attribute declaration for the unqualified name "priority", or contain a local element declaration for the name "address", without conflict or necessary relation between the two.
An element information item in an instance may , however, explicitly assert its type using the attribute xsi:type. An element so labeled must be empty, but can carry attributes if permitted by the corresponding complex type. Components are defined in terms of their properties, and each property in turn is defined by giving its range, that is the values it may have. This can be understood as defining a schema as a labeled directed graph, where the root is a schema, every other vertex is a schema component or a literal string, boolean, decimal and every labeled edge is a property.
Component properties are simply named values. Most properties have either other components or literals that is, strings or booleans or enumerated keywords for values, but in a few cases, where more complex values are involved, [Definition:] a property value may itself be a collection of named values, which we call a property record.
Again this should not be interpreted as constraining implementations, as for instance between using a null value for such properties or not representing them at all.
Any property value identified as a superset or subset of some set might be equal to that set, unless a proper superset or subset is explicitly called for.
The principal purpose of XML Schema Definition Language: Structures is to define a set of schema components that constrain the contents of instances and augment the information sets thereof. Although no external representation of schemas is required for this purpose, such representations will obviously be widely used.
To provide for this in an appropriate and interoperable way, this specification provides a normative XML representation for schemas which makes provision for every kind of schema component. A recurrent pattern in the XML representation of schemas may also be mentioned here. In many cases, the same element name e. In the first case the name attribute is required, in the second the ref attribute is required.
These two usages are mutually exclusive, and sometimes also depend on context. For each kind of schema component there is a corresponding normative XML representation. The language used is as if the correspondences were mappings from XML representation to schema component, but the mapping in the other direction, and therefore the correspondence in the abstract, can always be constructed therefrom.
In discussing the mapping from XML representations to schema components below, the value of a component property is often determined by the value of an attribute information item, one of the [attributes] of an element information item.
The associated datatype is, unless otherwise specified, the one identified in the declaration of the attribute, in the schema for schema documents; in some cases e. Many properties are identified below as having other schema components or sets of components as values.
For the purposes of exposition, the definitions in this section assume that unless the property is explicitly identified as optional all such values are in fact present.
Throughout this specification, [Definition:] the initial value of some attribute information item is the value of the [normalized value] property of that item.
Similarly, the initial value of an element information item is the string composed of, in order, the [character code] of each character information item in the [children] of that element information item. These three levels of normalization correspond to the processing mandated in XML for element content, CDATA attribute content and tokenized attributed content, respectively. Performing it twice in the case of attributes whose [normalized value] has already been subject to replacement or collapse on the basis of information in a DTD is necessary to ensure consistent treatment of attributes regardless of the extent to which DTD-based information has been made use of during infoset construction.
For an attribute declaration A , if A. Note that it is values that are checked, not strings, and that the test is for either equality or identity. No means is provided in this specification to supply a default value for a namespace declaration. Validators in a single file ts. ZipCodeValidator ;. LettersOnlyValidator ;. Contributors to this page: MH. We just had this issue where visual studio helpfully added a local reference rather than going via nuget.
Removing this and referencing via nuget solved the problem, looks like an issue in Visual Studio Mine was simply that I had not referenced Microsoft.
App in the. A plain dotnet restore didn't do the trick for me. I had to force a reevaluation of all dependencies like so:. My problem was that a project in the solution was not building properly, so it could not be referenced by other projects in the solution.
The solution was to update Visual Studio I updated from version Here is a link to Microsoft's VS Downloads page. I have found this problem when upgrading libraries from. NET Standard 2. NET Core 2. The best bet is just to redo all the NuGet includes for the project from scratch. Open the. I had this error upgrading a.
NET Core v2. Specifically, a unit testing project was giving the error, that didn't directly use the AspNetCore package. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Error CS The type or namespace name 'AspNetCore' does not exist in the namespace 'Microsoft' are you missing an assembly reference?
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