public abstract void Visit(DropForeignKeyCommand command);
 public override void Visit(DropForeignKeyCommand command)
 {
     _output.WriteLine("// Dropping foreign key {0}", command.Name);
 }
 public void Visit(DropForeignKeyCommand command)
 {
 }
 public SchemaBuilder DropForeignKey(string srcModule, string srcTable, string name)
 {
     var command = new DropForeignKeyCommand(String.Concat(_formatPrefix(srcModule), srcTable), name);
     Run(command);
     return this;
 }