我正在尝试从表中的表创建动态odata服务，这些服务在运行时才会知道。因此，在我的Web应用程序开始时，用户选择一个数据库，在C＃中我找到该数据库中的所有表。
现在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。编译时已知的数据库表有很多例子，但在这种情况下，直到我的用户第一次使用我的应用程序时才会有它们。
答案 0 :(得分：19)
有一个例子不需要预定义的类：ODataUntypedSample，但它确实需要一个预定义的控制器。
我已经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。我已经使用这个nuget包来读取数据库模式和数据：DatabaseSchemaReader。您需要以下nuget包才能构建它（以及依赖项）：
这是稍微修改的主程序，因此它从表中声明了Edm（用于OData）实体。我已经对标准样本Adventure Works 2014进行了测试，但它应该适用于任何表格：
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);
}
}
}
特殊的TableController和TableControllerSelector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：
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;
}
}
答案 1 :(得分：2)
1。您是否尝试过使用字典？我不知道它是否适用于OData，只是一个想法，因为我使用的各种数据连接/解串器也使用了字典。
2。我更多的想法是从数据源中检索一个类，我在这里发现了一些可能对您有帮助的内容：Class to DataSet / DataSet to class，也许如果没有存在更多障碍，使用返回的数据构建结构以将数据放入...
很抱歉因为某种方式不确定答案，只是想法来到我的脑海，我对OData一无所知。希望它有所帮助。