/// <summary>
/// Create a LearningStoreXml from some data within a row of a
/// LogableSqlCommand
/// </summary>
/// <param name="command">The LogableSqlCommand. The current position is
/// not modified.</param>
/// <param name="startingColumn">The index of the first column to be
/// examined. On exit, this index contains the last column examined
/// plus one.</param>
/// <returns>The <Typ>LearningStoreXml</Typ>, or null if a
/// value is not found.</returns>
/// <remarks>Only examines one column. Assumes that the column contains
/// an XML value. If the column is non-null, a LearningStoreXml
/// is returned. If the column is null, null is returned.
/// </remarks>
private static LearningStoreXml ReadXmlColumns(LogableSqlCommand command,
ref int startingColumn)
{
if (command.IsDBNull(startingColumn))
{
startingColumn++;
return(null);
}
else
{
SqlXml xml = command.GetSqlXml(startingColumn);
startingColumn++;
return(new LearningStoreXml(xml));
}
}
/// <summary>
/// Get the schema information for this store from the cache or from the database.
/// </summary>
/// <param name="connectionString">Connection string used to access the store.</param>
/// <param name="impersonationBehavior">Identifies which <c>WindowsIdentity</c> is used to
/// access the database when impersonation is involved.</param>
/// <param name="debugLog">Location to which the debug log should be written, or
/// null if there isn't a debug log.</param>
/// <returns>The schema information.</returns>
private static LearningStoreSchema GetSchemaInformationFromCache(string connectionString,
ImpersonationBehavior impersonationBehavior, TextWriter debugLog)
{
// Try to find the connection in the cache
lock (s_allSchemasLock)
{
LearningStoreSchema schema;
if (s_allSchemas.TryGetValue(connectionString, out schema))
{
return(schema);
}
}
// Not found in the cache -- so go get it from the database
// This try/catch block is here for security reasons. Search MSDN for
// "WrapVulnerableFinallyClausesInOuterTry" to see details.
try
{
WindowsImpersonationContext impersonationContext = null;
try
{
// Impersonate if necessary
if (impersonationBehavior == ImpersonationBehavior.UseOriginalIdentity)
{
// Not adding it to the disposer, since that could fail (e.g., OutOfMemoryException),
// which could cause a security hole. Instead, we'll clean it up manually later.
impersonationContext = WindowsIdentity.Impersonate(IntPtr.Zero);
}
using (Microsoft.LearningComponents.Disposer disposer = new Microsoft.LearningComponents.Disposer())
{
// Create a connection
SqlConnection connection = new SqlConnection(connectionString);
disposer.Push(connection);
connection.Open();
// Create a command to retrieve information from the configuration table
LogableSqlCommand command = new LogableSqlCommand(connection, debugLog);
disposer.Push(command);
// Execute
command.Execute(
"SELECT EngineVersion,\r\n" +
" SchemaDefinition\r\n" +
"FROM Configuration\r\n");
// Read return values from the database
if (!command.Read())
{
throw new LearningComponentsInternalException("LSTR1500");
}
if (command.GetFieldCount() != 2)
{
throw new LearningComponentsInternalException("LSTR1510");
}
int engineVersion = command.GetInt32(0);
SqlXml schemaXml = command.GetSqlXml(1);
XPathDocument schemaDoc;
using (XmlReader reader = schemaXml.CreateReader())
{
schemaDoc = new XPathDocument(reader);
}
LearningStoreSchema newSchema = LearningStoreSchema.CreateSchema(schemaDoc);
if (command.Read())
{
throw new LearningComponentsInternalException("LSTR1520");
}
if (command.NextResult())
{
throw new LearningComponentsInternalException("LSTR1530");
}
// Fail if a different engine created this
if (engineVersion != LearningStore.EngineVersion)
{
throw new InvalidOperationException(LearningStoreStrings.IncompatibleEngineVersion);
}
// Save it in the cache
lock (s_allSchemasLock)
{
LearningStoreSchema schema;
if (s_allSchemas.TryGetValue(connectionString, out schema))
{
return(schema);
}
s_allSchemas.Add(connectionString, newSchema);
}
return(newSchema);
}
}
finally
{
if (impersonationContext != null)
{
impersonationContext.Dispose();
}
}
}
catch
{
throw;
}
}