如何动态地创建predicate [英] How to create predicate dynamically

问题描述

我想创建一个基于搜索字符串列表，使用predicate EX pressions。

Hi i want to create a list based on the search string using predicate expressions.

我有型产品的列表中包含不同的名字。

I have a list of type products contains different names.

List<products> list1 = new List<products>();

        list1.Add(new products("sowmya"));
        list1.Add(new products("Jane"));
        list1.Add(new products("John"));
        list1.Add(new products("kumar"));
        list1.Add(new products("ramya"));
        listBox1.ItemsSource = list1;

现在我想筛选基于用户input.User将进入N无串用'+'作为分隔符的内容。接到字符串后，我将它们传递到这样的predicate对象

Now i want to filter the content based on user input.User will enter n no of strings with '+' as separator. After receiving the strings i will pass them to predicate object like this

 private void textBox1_KeyDown(object sender, KeyEventArgs e)
    {
        List<products> list2 = new List<products>();
        Expression<Func<products, bool>> predicate = PredicateBuilder.True<products>();
        if (e.Key == Key.Enter)
        {
            string Searchstring = textBox1.Text.ToString().Trim();
            string[] separator = new string[] { "+" };
            string[] SearchItems=Searchstring.Split(separator,StringSplitOptions.None);
            foreach (string str in SearchItems)
            {
                string temp = str;
                predicate =p => p.Name.Contains(temp.ToLower());                   
            }

            list2 = list1.AsQueryable().Where(predicate).ToList();
            listBox1.ItemsSource = list2;
        }
    }

如果我输入了多个字符串（sowmya +简+约翰），其只给最后一个字符串（约翰）的结果，但我想所有匹配的字符串列表

If i enter more than one string(sowmya+jane+john) its giving only the last string(john) result but i want a list of all matching strings

请回答这个问题，因为我想这一点，但我无法得到的结果。

Please answer this question because i'm trying this but i couldn't get the result.

请做一定的帮助表示感谢。

Please do some help thanks.

推荐答案

初始化predicate假

Initialize the predicate as false

Expression<Func<products, bool>> predicate = PredicateBuilder.False<products>();

您需要使用相结合的predicates 或

You need to combine the predicates using Or

foreach (string str in SearchItems)
{
    string temp = str;
    predicate = predicate.Or(p => p.NameToLower().Contains(temp.ToLower()));                   
}

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