Dynamic odata service in C# from runtime data layer
There is an example that doesn't require a predefined class available here: ODataUntypedSample, but it does require a predefined controller.
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
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);
}
}
}
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;
}
}
1. Have you tried using a dictionary? I don't know if it works with OData, just an idea which came up as all kinds of data connection/deserialisers I've worked with also worked with dictionary.
2. The idea I'm more into, is to retrieve a class from the data source, I found something here that might help you: Class to DataSet / DataSet to class, maybe if no more obstacles exist, using the data returned to build a structure to put data inside ...
Sorry for being somehow uncertain about the answers, just ideas came to my head, I don't know much about OData. Hope it helped.