Unable to inherit 'SqlScriptGenerator' class

Beginne mit den im Issue gezeigten Signaturen von SqlScriptGenerator, SqlScriptGeneratorVisitor, ScriptWriter und Sql100ScriptGenerator. Überprüfe, wie Visitor und Writer derzeit erstellt werden, und ermittle anschließend die erforderlichen Änderungen an der öffentlichen/geschützten API, damit eine externe Unterklasse kompiliert werden kann. Erledigt ist dies, wenn ein benutzerdefiniertes SqlScriptGenerator erben und die Visitor-Factory überschreiben kann, ohne sich auf interne Typen zu stützen.

Is your feature request related to a problem? Please describe.

Consider the following code to inherit SqlScriptGenerator

internal class CustomSqlScriptGenerator : SqlScriptGenerator
{
	public CustomSqlScriptGenerator(SqlScriptGeneratorOptions options) : base(options)
	{
	}

	internal override SqlScriptGeneratorVisitor CreateSqlScriptGeneratorVisitor(SqlScriptGeneratorOptions options, ScriptWriter scriptWriter)
	{
		throw new NotImplementedException();
	}
}

However, this will get compilation error because SqlScriptGeneratorVisitor and ScriptWriter are marked as internal, which is impossible to inherit this class.

Describe the solution you'd like

• Change CreateSqlScriptGeneratorVisitor(...) become protected instead of internal
• Remove ScriptWriter parameter in CreateSqlScriptGeneratorVisitor(...). This can avoid to mark ScriptWriter as public. Instantiation of ScriptWriter will be handled by child class of SqlScriptGenerator. See example below.
• Mark SqlScriptGeneratorVisitor as public accessible. SqlScriptGeneratorVisitor will be used to visit the expression tree when generating TSQL script.

Here is the suggested changes:

protected abstract SqlScriptGeneratorVisitor CreateSqlScriptGeneratorVisitor(SqlScriptGeneratorOptions options);

And update Sql###ScriptGenerator become

Example:

public sealed class Sql100ScriptGenerator : SqlScriptGenerator
{
    public Sql100ScriptGenerator()
        : this(new SqlScriptGeneratorOptions())
    {
    }

    public Sql100ScriptGenerator(SqlScriptGeneratorOptions options)
        : base(options)
    {
    }

    protected override SqlScriptGeneratorVisitor CreateSqlScriptGeneratorVisitor(SqlScriptGeneratorOptions options)
    {
        // Create instance of ScriptWriter. 
        //Currently this is created by private function in SqlScriptGenerator
        ScriptWriter scriptWriter = new ScriptWriter(options);

        ScriptGeneratorSupporter.CheckForNullReference((object) options, nameof (options));
        ScriptGeneratorSupporter.CheckForNullReference((object) scriptWriter, nameof (scriptWriter));
        return (SqlScriptGeneratorVisitor) new Sql100ScriptGeneratorVisitor(options, scriptWriter);
    }
}