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;
}