How can I create a MetadataWorkspace using metadata loading delegates? - runtime

Question

I followed this example Changing schema name on runtime - Entity Framework where I can create a new EntityConnection from a MetaDataWorkspace that I then use to construct a DbContext with a different schema, but I get compiler warnings saying that RegisterItemCollection method is obsolete and to "Construct MetadataWorkspace using constructor that accepts metadata loading delegates."
How do I do that? Here is the code that is working but gives the 3 warnings for the RegsiterItemCollection calls. I'm surprised it works since warning says obsolete not just deprecated.
public static EntityConnection CreateEntityConnection(string schema, string connString, string model)
{
XmlReader[] conceptualReader = new XmlReader[]
{
XmlReader.Create(
Assembly
.GetExecutingAssembly()
.GetManifestResourceStream(model + ".csdl")
)
};
XmlReader[] mappingReader = new XmlReader[]
{
XmlReader.Create(
Assembly
.GetExecutingAssembly()
.GetManifestResourceStream(model + ".msl")
)
};
var storageReader = XmlReader.Create(
Assembly
.GetExecutingAssembly()
.GetManifestResourceStream(model + ".ssdl")
);
//XNamespace storageNS = "http://schemas.microsoft.com/ado/2009/02/edm/ssdl"; // this would not work!!!
XNamespace storageNS = "http://schemas.microsoft.com/ado/2009/11/edm/ssdl";
var storageXml = XElement.Load(storageReader);
foreach (var entitySet in storageXml.Descendants(storageNS + "EntitySet"))
{
var schemaAttribute = entitySet.Attributes("Schema").FirstOrDefault();
if (schemaAttribute != null)
{
schemaAttribute.SetValue(schema);
}
}
storageXml.CreateReader();
StoreItemCollection storageCollection =
new StoreItemCollection(
new XmlReader[] { storageXml.CreateReader() }
);
EdmItemCollection conceptualCollection = new EdmItemCollection(conceptualReader);
StorageMappingItemCollection mappingCollection =
new StorageMappingItemCollection(
conceptualCollection, storageCollection, mappingReader
);
//var workspace2 = new MetadataWorkspace(conceptualCollection, storageCollection, mappingCollection);
var workspace = new MetadataWorkspace();
workspace.RegisterItemCollection(conceptualCollection);
workspace.RegisterItemCollection(storageCollection);
workspace.RegisterItemCollection(mappingCollection);
var connectionData = new EntityConnectionStringBuilder(connString);
var connection = DbProviderFactories
.GetFactory(connectionData.Provider)
.CreateConnection();
connection.ConnectionString = connectionData.ProviderConnectionString;
return new EntityConnection(workspace, connection);
}

Answer 1

I was able to get rid of the 3 warning messages. Basically it wants you to register the collections in the constructor of the MetadataWorkspace.
There are 3 different overloads for MetadataWorkspace, I chose to use the one which requires to to supply a path (array of strings) to the workspace metadata. To do this I saved readers to temp files and reloaded them.
This is working for me without any warnings.
public static EntityConnection CreateEntityConnection(string schema, string connString, string model) {
var conceptualReader = XmlReader.Create(Assembly.GetExecutingAssembly().GetManifestResourceStream(model + ".csdl"));
var mappingReader = XmlReader.Create(Assembly.GetExecutingAssembly().GetManifestResourceStream(model + ".msl"));
var storageReader = XmlReader.Create(Assembly.GetExecutingAssembly().GetManifestResourceStream(model + ".ssdl"));
XNamespace storageNS = "http://schemas.microsoft.com/ado/2009/11/edm/ssdl";
var storageXml = XElement.Load(storageReader);
var conceptualXml = XElement.Load(conceptualReader);
var mappingXml = XElement.Load(mappingReader);
foreach (var entitySet in storageXml.Descendants(storageNS + "EntitySet")) {
var schemaAttribute = entitySet.Attributes("Schema").FirstOrDefault();
if (schemaAttribute != null) {
schemaAttribute.SetValue(schema);
}
}
storageXml.Save("temp.ssdl");
conceptualXml.Save("temp.csdl");
mappingXml.Save("temp.msl");
MetadataWorkspace workspace = new MetadataWorkspace(new List<String>(){
#"temp.csdl",
#"temp.ssdl",
#"temp.msl"
}
, new List<Assembly>());
var connectionData = new EntityConnectionStringBuilder(connString);
var connection = DbProviderFactories.GetFactory(connectionData.Provider).CreateConnection();
connection.ConnectionString = connectionData.ProviderConnectionString;
return new EntityConnection(workspace, connection);
}

Answer 2

Not wanting to create temp files which slows the process down, I found an alternate answer to this is fairly simple. I replaced these lines of code -
//var workspace2 = new MetadataWorkspace(conceptualCollection, storageCollection, mappingCollection);
var workspace = new MetadataWorkspace();
workspace.RegisterItemCollection(conceptualCollection);
workspace.RegisterItemCollection(storageCollection);
workspace.RegisterItemCollection(mappingCollection);
with this one line of code -
var workspace = new MetadataWorkspace(() => conceptualCollection, () => storageCollection, () => mappingCollection);
and that works fine.