来自运行时数据层的C#中的动态odata服务 [英] Dynamic odata service in C# from runtime data layer
问题描述
我正在尝试从我的表中的表创建动态的odata服务，直到运行时才知道这些表.因此，在我的Web应用程序开始时，用户选择一个数据库，然后在C#中找到该数据库中的所有表.
I'm trying to create a dynamic odata service from tables in my tables which are not known till runtime. So at the start of my web application, a user selects a database and in C# I find all the tables in that database.
现在最困难的部分是我想为数据库中的每个表创建odata服务端点，并在我的Web应用程序中相应地使用它们.问题是我不知道如何动态地做到这一点.有很多带有编译时已知数据库表的示例，但是在这种情况下，直到用户第一次使用我的应用程序时，我才会使用它们.
Now the hard part is I want to create odata service endpoints for each table in the database and use them accordingly in my web application. The problem is I don't know how to do it dynamically. There are lots of examples with compile time known database tables, but in this case, I won't have them till the first time my user uses my application.
推荐答案
There is an example that doesn't require a predefined class available here: ODataUntypedSample, but it does require a predefined controller.
我在其上构建了另一个控制台应用程序示例，以便能够使用OData查询任何SQL Server数据库.我已使用此nuget包读取数据库架构和数据: DatabaseSchemaReader .您需要以下nuget软件包才能构建它(加上依赖项):
I have built on it another console application sample to be able to query any SQL server database using OData. I've used this nuget package to read the database schema and data: DatabaseSchemaReader. You'll need the following nuget package to be able to build it (plus dependencies):
- Microsoft.Owin.Hosting
- Microsoft.Owin.Host.HttpListener
- Microsoft.AspNet.WebApi.Owin
- Microsoft.AspNet.OData
这里是主程序，它经过了一些修改，因此从表中声明了Edm(对于OData)实体.我已经测试了标准示例 Adventure Works 2014 ，但它有望在任何表上运行:
Here is the main program slightly modified so it declares Edm (for OData) entities from tables. I've tested the standard sample Adventure Works 2014 but it should work on any table hopefully:
class Program
{
private static HttpClient client = new HttpClient();
private static TableControllerSelector selector;
private const string ServiceUrl = "http://localhost:12345";
private const string connectionString = @"Server=MYSQLSERVER;Database=AdventureWorks2014;Integrated Security=SSPI";
static void Main(string[] args)
{
using (WebApp.Start(ServiceUrl, Configuration))
{
Console.WriteLine("Server is listening at {0}", ServiceUrl);
RunSample();
Console.WriteLine("Press any key to continue . . .");
Console.ReadKey();
}
}
public static void Configuration(IAppBuilder builder)
{
HttpConfiguration configuration = new HttpConfiguration();
// create a special dynamic controller selector
selector = new TableControllerSelector(configuration);
IEdmModel model = TableController.GetEdmModel(connectionString, selector);
configuration.Services.Replace(typeof(IHttpControllerSelector), selector);
configuration.MapODataServiceRoute("odata", "odata", model); // needs using System.Web.OData.Extensions
builder.UseWebApi(configuration);
}
public static void RunSample()
{
Console.WriteLine("1. Get Metadata.");
GetMetadata();
Console.WriteLine("\n2. Get Entity Set.");
using (var dbReader = new DatabaseReader(connectionString, "System.Data.SqlClient"))
{
foreach (var table in dbReader.AllTables())
{
Console.WriteLine("\n 2.1 Get Entity Set '" + table.Name + "'.");
GetEntitySet(table.Name);
}
}
}
public static void GetMetadata()
{
HttpResponseMessage response = client.GetAsync(ServiceUrl + "/odata/$metadata").Result;
PrintResponse(response);
}
public static void GetEntitySet(string tableName)
{
HttpResponseMessage response = client.GetAsync(ServiceUrl + "/odata/" + tableName + "?$filter=Id eq 1").Result;
PrintResponse(response);
}
public static void PrintResponse(HttpResponseMessage response)
{
response.EnsureSuccessStatusCode();
Console.WriteLine("Response:");
Console.WriteLine(response);
if (response.Content != null)
{
Console.WriteLine(response.Content.ReadAsStringAsync().Result);
}
}
}
还有特殊的TableController和TableControllerSelector类，这些类允许从任何SQL Server数据库创建Edm模型，并从该模型中的Edm实体动态创建控制器:
And the special TableController and TableControllerSelector classes that allow to create an Edm model from any SQL Server database, and create controllers dynamically from the Edm entities in that model:
public class TableControllerSelector : DefaultHttpControllerSelector
{
private Dictionary<string, HttpControllerDescriptor> _tables = new Dictionary<string, HttpControllerDescriptor>(StringComparer.OrdinalIgnoreCase);
public TableControllerSelector(HttpConfiguration configuration)
: base(configuration)
{
Configuration = configuration;
}
public HttpConfiguration Configuration { get; private set; }
public override HttpControllerDescriptor SelectController(HttpRequestMessage request)
{
string name = GetControllerName(request);
if (name != null) // is it a known table name?
{
HttpControllerDescriptor desc;
if (_tables.TryGetValue(name, out desc))
return desc;
}
return base.SelectController(request);
}
public void AddTable(string connectionString, DatabaseTable table)
{
if (connectionString == null)
throw new ArgumentNullException("connectionString");
if (table == null)
throw new ArgumentNullException("table");
// create a descriptor with extra properties that the controller needs
var desc = new HttpControllerDescriptor(Configuration, table.Name, typeof(TableController));
desc.Properties["table"] = table;
desc.Properties["connectionString"] = connectionString;
_tables[table.Name] = desc;
}
}
public class TableController : ODataController
{
// this will be called for standard OData access to collection
public EdmEntityObjectCollection Get()
{
// get Edm type from request
ODataPath path = Request.ODataProperties().Path; // ODataProperties() needs using System.Web.OData.Extensions
IEdmType edmType = path.EdmType;
IEdmCollectionType collectionType = (IEdmCollectionType)edmType;
IEdmEntityType entityType = (IEdmEntityType)collectionType.ElementType.Definition;
IEdmModel model = Request.ODataProperties().Model;
ODataQueryContext queryContext = new ODataQueryContext(model, entityType, path);
ODataQueryOptions queryOptions = new ODataQueryOptions(queryContext, Request);
// TODO: apply the query option on the IQueryable here.
// read all rows from table (could be optimized using query context)
var table = (DatabaseTable)ControllerContext.ControllerDescriptor.Properties["table"];
var cnx = (string)ControllerContext.ControllerDescriptor.Properties["connectionString"];
return new EdmEntityObjectCollection(new EdmCollectionTypeReference(collectionType), ReadData(entityType, table, cnx));
}
public static IList<IEdmEntityObject> ReadData(IEdmEntityType type, DatabaseTable table, string connectionString)
{
List<IEdmEntityObject> list = new List<IEdmEntityObject>();
// https://www.nuget.org/packages/DatabaseSchemaReader/
Reader reader = new Reader(table, connectionString, "System.Data.SqlClient");
reader.Read((r) =>
{
EdmEntityObject obj = new EdmEntityObject(type);
foreach (var prop in type.DeclaredProperties)
{
int index = r.GetOrdinal(prop.Name);
object value = r.GetValue(index);
if (Convert.IsDBNull(value))
{
value = null;
}
obj.TrySetPropertyValue(prop.Name, value);
}
list.Add(obj);
// uncomment these 2 lines if you're just testing maximum 10 rows on a table
//if (list.Count == 10)
// return false;
return true;
});
return list;
}
public static IEdmModel GetEdmModel(string connectionString, TableControllerSelector selector)
{
EdmModel model = new EdmModel();
// create and add entity container
EdmEntityContainer container = new EdmEntityContainer("NS", "DefaultContainer");
model.AddElement(container);
// https://www.nuget.org/packages/DatabaseSchemaReader/
using (var dbReader = new DatabaseReader(connectionString, "System.Data.SqlClient"))
{
var schema = dbReader.ReadAll();
foreach (var table in schema.Tables)
{
EdmEntityType tableType = new EdmEntityType("NS", table.Name);
foreach (var col in table.Columns)
{
var kind = GetKind(col);
if (!kind.HasValue) // don't map this
continue;
var prop = tableType.AddStructuralProperty(col.Name, kind.Value, col.Nullable);
if (col.IsPrimaryKey)
{
tableType.AddKeys(prop);
}
}
model.AddElement(tableType);
EdmEntitySet products = container.AddEntitySet(table.Name, tableType);
selector.AddTable(connectionString, table);
}
}
return model;
}
// determine Edm kind from column type
private static EdmPrimitiveTypeKind? GetKind(DatabaseColumn col)
{
var dt = col.DataType;
if (col.DataType == null)
return null;
Type type = col.DataType.GetNetType();
if (type == null)
return null;
if (type == typeof(string))
return EdmPrimitiveTypeKind.String;
if (type == typeof(short))
return EdmPrimitiveTypeKind.Int16;
if (type == typeof(int))
return EdmPrimitiveTypeKind.Int32;
if (type == typeof(long))
return EdmPrimitiveTypeKind.Int64;
if (type == typeof(bool))
return EdmPrimitiveTypeKind.Boolean;
if (type == typeof(Guid))
return EdmPrimitiveTypeKind.Guid;
if (type == typeof(DateTime))
return EdmPrimitiveTypeKind.DateTimeOffset;
if (type == typeof(TimeSpan))
return EdmPrimitiveTypeKind.Duration;
if (type == typeof(decimal))
return EdmPrimitiveTypeKind.Decimal;
if (type == typeof(byte) || type == typeof(sbyte))
return EdmPrimitiveTypeKind.Byte;
if (type == typeof(byte[]))
return EdmPrimitiveTypeKind.Binary;
if (type == typeof(double))
return EdmPrimitiveTypeKind.Double;
if (type == typeof(float))
return EdmPrimitiveTypeKind.Single;
return null;
}
}
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