您可以更優雅的完成你的任務,積累了這樣的過濾器表達式:
Expression<Func<PersonalInfo, bool>> filterExperssion = PredicateExtensions.True<PersonalInfo>();
if (!String.IsNullOrEmpty(firstName))
filterExperssion = filterExperssion.And(p => p.FirstName == firstName);
if (!String.IsNullOrEmpty(lastName))
......
你需要這個小類幫手建立謂詞
public static class PredicateExtensions
{
public static Expression<Func<T, bool>> True<T>() { return f => true; }
public static Expression<Func<T, bool>> False<T>() { return f => false; }
public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expression1, Expression<Func<T, bool>> expression2)
{
var invokedExpression = Expression.Invoke(expression2, expression1.Parameters.Cast<Expression>());
return Expression.Lambda<Func<T, bool>>
(Expression.Or(expression1.Body, invokedExpression), expression1.Parameters);
}
public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expression1,
Expression<Func<T, bool>> expression2)
{
var invokedExpression = Expression.Invoke(expression2, expression1.Parameters.Cast<Expression>());
return Expression.Lambda<Func<T, bool>>
(Expression.And(expression1.Body, invokedExpression), expression1.Parameters);
}
}
linq to objects or linq to sql? – devundef 2012-08-08 10:22:57
@devundef - OP提到數據來自文件。似乎沒有ORM參與。 – Oded 2012-08-08 10:25:08
@devundef - 在這種情況下,我沒有使用ORM。 – user1260827 2012-08-08 10:32:57