SqlPreCommand

Signum Engine is all about generating Sql commands. Usually these commands are big strings and expensive to concatenate. StringBuilder, on the other hand, is more efficient but tends to generate code in a very imperative way.

In order to have a good balance between usability (functional style) and performance, SqlPreCommand was created.

SqlPreCommand is an abstract class, there are two implementations: SqlPreCommandSimple and SqlPreCommandConcat.

In memory, SqlPreCommands is a tree with SqlPreCommandSimple on the leaves, and SqlPreCommandConcat mixing them. At the very end, when the command is going to be executed, the tree gets flattened once in a efficient way, or the leaves are executed one by one independently.

Contains a piece of sql text, consistent and executable by itself. Also, contains a list with all the related SqlParameter objects to execute it (to avoid SQL injection attack)

It has a pair of constructors like this:

public SqlPreCommandSimple(string sql)
public SqlPreCommandSimple(string sql, List<DbParameter> parameters)

Contains an array with all the SqlPreCommand (Simple or Concat), as well as a value of the Spacing enum to determine how many blank lines will be rendered between commands.

It has no public constructor, instead the static method Combine in SqlPreCommand should be used instead. It's defined like this:

public static SqlPreCommand Combine(Spacing spacing, params SqlPreCommand[] sentences)
{
    if (sentences.Contains(null))
        sentences = sentences.NotNull().ToArray();

    if (sentences.Length == 0)
        return null;

    if (sentences.Length == 1)
        return sentences[0];

    return new SqlPreCommandConcat(spacing, sentences);
}

There's also another overloading over any IEnumerable<SqlPrecommand> using extension methods:

public static SqlPreCommand Combine(this IEnumerable<SqlPreCommand> preCommands, Spacing spacing)
{
    return SqlPreCommand.Combine(spacing, preCommands.ToArray());
}

Turns a SqlPreCommand into a SqlPreCommandSimple. In case of being SqlPreCommandConcat, concatenates the sql queries and the parameters. SqlPreCommandSimple just returns itself. Use ToSimple, not casting.

Returns a string with all the SqlParameter inlined in the SQL commands. Good for debugging or generating scripts, but not for production code because it's sensitive to SQL Injection attacks.