/// <summary>
/// Translates a given predicate for a given related type.
/// </summary>
/// <typeparam name="TTranslatedSource">The type of the translated predicate's parameter.</typeparam>
/// <param name="path">The path from the desired type to the given type.</param>
/// <returns>A translated predicate expression.</returns>
public Expression <Func <TTranslatedSource, bool> > To <TTranslatedSource>(Expression <Func <TTranslatedSource, TSource> > path)
{
if (path == null)
{
throw new ArgumentNullException(nameof(path));
}
var s = _predicate.Parameters[0];
var t = path.Parameters[0];
var binder = new ReplaceExpressionVisitor(s, path.Body);
return(Expression.Lambda <Func <TTranslatedSource, bool> >(
binder.Visit(_predicate.Body), t));
}
/// <summary>
/// Translates a given predicate for a given related type.
/// </summary>
/// <typeparam name="TTranslatedSource">The type of the translated predicate's parameter.</typeparam>
/// <param name="translation">The translation from the desired type to the given type,
/// using the initially given predicate to be injected into a new predicate.</param>
/// <returns>A translated predicate expression.</returns>
public Expression <Func <TTranslatedSource, bool> > To <TTranslatedSource>(Expression <Func <TTranslatedSource, Func <TSource, bool>, bool> > translation)
{
if (translation == null)
{
throw new ArgumentNullException(nameof(translation));
}
var t = translation.Parameters[0];
var s = translation.Parameters[1];
var binder = new ReplaceExpressionVisitor(s, _predicate);
return(Expression.Lambda <Func <TTranslatedSource, bool> >(
binder.Visit(translation.Body), t));
}
private static Expression <Func <T, bool> > AndAlso <T>(
this Expression <Func <T, bool> > expr1,
Expression <Func <T, bool> > expr2,
Func <Expression, Expression, BinaryExpression> func)
{
var parameter = Expression.Parameter(typeof(T));
var leftVisitor = new ReplaceExpressionVisitor(expr1.Parameters[0], parameter);
var left = leftVisitor.Visit(expr1.Body);
var rightVisitor = new ReplaceExpressionVisitor(expr2.Parameters[0], parameter);
var right = rightVisitor.Visit(expr2.Body);
return(Expression.Lambda <Func <T, bool> >(
func(left, right), parameter));
}
public static Expression Replace(this Expression baseExpression, Expression search, Expression replace)
{
var visitor = new ReplaceExpressionVisitor(search, replace);
return(visitor.Visit(baseExpression));
}
