这篇文章主要为大家展示了“.NET Core开发日志之OData的示例分析”，内容简而易懂，条理清晰，希望能够帮助大家解决疑惑，下面让小编带领大家一起研究并学习一下“.NET Core开发日志之OData的示例分析”这篇文章吧。
简述
OData，即Open Data Protocol，是由微软在2007年推出的一款开放协议，旨在通过简单、标准的方式创建和使用查询式及交互式RESTful API。
类库
在.NET Core中想要使用OData功能的话需要添加Microsoft.AspNetCore.OData包。
dotnet add package Microsoft.AspNetCore.OData
准备模型类
public class Address
{
public string City { get; set; }
public string Street { get; set; }
}
public enum Category
{
Book,
Magazine,
EBook
}
public class Press
{
public int Id { get; set; }
public string Name { get; set; }
public string Email { get; set; }
public Category Category { get; set; }
}
public class Book
{
public int Id { get; set; }
public string ISBN { get; set; }
public string Title { get; set; }
public string Author { get; set; }
public decimal Price { get; set; }
public Address Address { get; set; }
public Press Press { get; set; }
}创建Edm模型
OData使用EDM，即Entity Data Model来描述数据的结构。在Startup文件中添加创建方法。
private static IEdmModel GetEdmModel()
{
var builder = new ODataConventionModelBuilder();
builder.EntitySet<Book>("Books");
builder.EntitySet<Press>("Presses");
return builder.GetEdmModel();
}注册OData服务
在Startup文件的ConfigureServices方法里注册OData服务。
services.AddOData();
services.AddMvc(options =>
{
options.EnableEndpointRouting = false;
}).SetCompatibilityVersion(CompatibilityVersion.Version_2_2);这里要注意的是在.NET Core 2.2里，默认已经有终结点，所以要使用OData的终结点的话需要将默认选项禁用掉。
注册OData终结点
同样在Startup文件里，在其Configure方法内将原来的注册路由内容改为注册OData的终结点。
app.UseMvc(b =>
{
b.MapODataServiceRoute("odata", "odata", GetEdmModel());
});显示元数据
运行程序后访问https://localhost:5001/odata/$metadata地址，可以看到所有可用模型的元数据。
<edmx:Edmx xmlns:edmx="http://docs.oasis-open.org/odata/ns/edmx" Version="4.0"> <edmx:DataServices> <Schema xmlns="http://docs.oasis-open.org/odata/ns/edm" Namespace="Default"> <EntityType Name="Book"> <Key> <PropertyRef Name="Id"/> </Key> <Property Name="Id" Type="Edm.Int32" Nullable="false"/> <Property Name="ISBN" Type="Edm.String"/> <Property Name="Title" Type="Edm.String"/> <Property Name="Author" Type="Edm.String"/> <Property Name="Price" Type="Edm.Decimal" Nullable="false"/> <Property Name="Address" Type="Default.Address"/> <NavigationProperty Name="Press" Type="Default.Press"/> </EntityType> <EntityType Name="Press"> <Key> <PropertyRef Name="Id"/> </Key> <Property Name="Id" Type="Edm.Int32" Nullable="false"/> <Property Name="Name" Type="Edm.String"/> <Property Name="Email" Type="Edm.String"/> <Property Name="Category" Type="Default.Category" Nullable="false"/> </EntityType> <ComplexType Name="Address"> <Property Name="City" Type="Edm.String"/> <Property Name="Street" Type="Edm.String"/> </ComplexType> <EnumType Name="Category"> <Member Name="Book" Value="0"/> <Member Name="Magazine" Value="1"/> <Member Name="EBook" Value="2"/> </EnumType> <EntityContainer Name="Container"> <EntitySet Name="Books" EntityType="Default.Book"> <NavigationPropertyBinding Path="Press" Target="Presses"/> </EntitySet> <EntitySet Name="Presses" EntityType="Default.Press"/> </EntityContainer> </Schema> </edmx:DataServices> </edmx:Edmx>
创建Controller
本文实例中不考虑数据库的操作，故而使用hard code方式构建必要的模型对象。
public class BooksController : ODataController
{
private static IList<Book> Books {get; set;}
public BooksController()
{
Books = new List<Book>
{
new Book
{
Id = 1,
ISBN = "111-0-321-56789-1",
Title = "Calculus",
Price = 66.6m,
Address = new Address
{
City = "Shanghai",
Street = "Beijin Xi Road"
},
Press = new Press
{
Id = 1,
Name = "Shanghai Tongji",
Category = Category.Book
}
},
new Book
{
Id = 2,
ISBN = "222-2-654-00000-2",
Title = "Linear Algebra",
Price = 53.2m,
Address = new Address
{
City = "Shanghai",
Street = "Beijin Dong Road"
},
Press = new Press
{
Id = 2,
Name = "Shanghai Fudan",
Category = Category.EBook
}
}
};
}
[EnableQuery]
public IActionResult Get()
{
return Ok(Books);
}
[EnableQuery]
public IActionResult Get(int key)
{
return Ok(Books.FirstOrDefault(b => b.Id == key));
}
}EnableQuery特性在需要高级查询的场景时必须添加。
查询
加入Controller之后，访问https://localhost:5001/odata/Books地址，可得到所有Book数据。
{
"@odata.context": "https://localhost:5001/odata/$metadata#Books",
"value": [
{
"Id": 1,
"ISBN": "111-0-321-56789-1",
"Title": "Calculus",
"Author": null,
"Price": 66.6,
"Address": {
"City": "Shanghai",
"Street": "Beijin Xi Road"
}
},
{
"Id": 2,
"ISBN": "222-2-654-00000-2",
"Title": "Linear Algebra",
"Author": null,
"Price": 53.2,
"Address": {
"City": "Shanghai",
"Street": "Beijin Dong Road"
}
}
]
}访问https://localhost:5001/odata/Books(1)地址，可得到key值为1的Book数据。
{
"@odata.context": "https://localhost:5001/odata/$metadata#Books/$entity",
"Id": 1,
"ISBN": "111-0-321-56789-1",
"Title": "Calculus",
"Author": null,
"Price": 66.6,
"Address": {
"City": "Shanghai",
"Street": "Beijin Xi Road"
}
}高级查询
如果想要使用OData查询的高级功能，可以在注册终结点时额外加上相应的配置。
app.UseMvc(b =>
{
b.Select().Expand().Filter().OrderBy().MaxTop(100).Count();
b.MapODataServiceRoute("odata", "odata", GetEdmModel());
});访问网址时加上所需的查询内容：
https://localhost:5001/odata/Books?$select=Id,Title
{
"@odata.context": "https://localhost:5001/odata/$metadata#Books(Id,Title)",
"value": [
{
"Id": 1,
"Title": "Calculus"
},
{
"Id": 2,
"Title": "Linear Algebra"
}
]
}如果想要按特定条件过滤数据内容的话也很容易：
https://localhost:5001/odata/Books?$filter=Price%20le%2060
{
"@odata.context": "https://localhost:5001/odata/$metadata#Books",
"value": [
{
"Id": 2,
"ISBN": "222-2-654-00000-2",
"Title": "Linear Algebra",
"Author": null,
"Price": 53.2,
"Address": {
"City": "Shanghai",
"Street": "Beijin Dong Road"
}
}
]
}以上是“.NET Core开发日志之OData的示例分析”这篇文章的所有内容，感谢各位的阅读！相信大家都有了一定的了解，希望分享的内容对大家有所帮助，如果还想学习更多知识，欢迎关注亿速云行业资讯频道！
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