public static Expression GetBodyWithNewParameter <T>(
LambdaExpression expression,
ParameterExpression parameter)
{
if (parameter.Type != typeof(T))
{
throw new ArgumentException($@"The parameter type {parameter.Type.Name} is not valid for the provided expression");
}
var visitor = new ReplaceParameter1Visitor(
expression.Parameters.First(), parameter);
return(visitor.Visit(expression.Body));
}
public static Expression <Func <T, bool> > Inject <T>(Expression <Func <T, bool> > predicate,
Expression <Action <T> > lambdaTrue, Expression <Action <T> > lambdaFalse)
{
if (predicate.ReturnType != typeof(bool) &&
predicate.Parameters.Count != 1)
{
throw new ArgumentException("The predicate must be a Func<T, bool>");
}
if ((lambdaTrue != null && lambdaTrue.Parameters.Count != predicate.Parameters.Count) ||
(lambdaFalse != null && lambdaFalse.Parameters.Count != predicate.Parameters.Count))
{
throw new ArgumentException("Lambdas cannot accept input parameters");
}
var inputParameter = predicate.Parameters.Single();
if (lambdaTrue != null)
{
lambdaTrue = Expression.Lambda <Action <T> >(
ReplaceParameter1Visitor.GetBodyWithNewParameter <T>(
lambdaTrue, inputParameter), inputParameter);
}
if (lambdaFalse != null)
{
lambdaFalse = Expression.Lambda <Action <T> >(
ReplaceParameter1Visitor.GetBodyWithNewParameter <T>(
lambdaFalse, inputParameter), inputParameter);
}
Expression callTrue = lambdaTrue == null?
Expression.Empty() : lambdaTrue.Body;
Expression callFalse = lambdaFalse == null?
Expression.Empty() : lambdaFalse.Body;
return(Inject(predicate, callTrue, callFalse));
}
