public static Geodatabase CreateGeodatabase( 
   MemoryConnectionProperties memoryConnectionProperties
)

public void CreateMemoryGeodatabaseSnippet()
{
  // Create the memory connection properties to connect to  default memory geodatabase
  MemoryConnectionProperties memoryConnectionProperties = new MemoryConnectionProperties();

  // Alternatively create the memory connection properties to connect to memory geodatabase named as 'InterimMemoryGeodatabase'
  // MemoryConnectionProperties memoryConnectionProperties = new MemoryConnectionProperties("InterimMemoryGeodatabase");

  // Creates the new memory geodatabase if it does not exist or connects to an existing one if it already exists
  using (Geodatabase geodatabase = new Geodatabase(memoryConnectionProperties))
  {
    // Create additional schema here
  }
}

public Geodatabase GetMemoryGeodatabase()
{
  // Creates the default memory geodatabase if not exist or connects to an existing one if already exists
  Geodatabase memoryGeodatabase = new Geodatabase(new MemoryConnectionProperties());

  // Creates schema
  SchemaBuilder schemaBuilder = new SchemaBuilder(memoryGeodatabase);
  schemaBuilder.Create(new TableDescription("MyTable", new List<FieldDescription>()));
  schemaBuilder.Build();

  return memoryGeodatabase;
}