(C#)表达式树-创新互联
例如: bool result = (key1==val1) || (key2!=val2) && (key3==val3). 其中 keyN, valN 均为变量。
创新互联专注于企业成都全网营销推广、网站重做改版、黄山区网站定制设计、自适应品牌网站建设、成都h5网站建设、商城网站定制开发、集团公司官网建设、成都外贸网站制作、高端网站制作、响应式网页设计等建站业务,价格优惠性价比高,为黄山区等各大城市提供网站开发制作服务。基本的思路是先做Express string 验证,然后进行解析。
验证可以用正则表达式。
解析最基本的方法是用 表达式树 (Express Tree). PostFix.
C# linq 提供了一个解决方案就是 Linq 语法树。
https://www.codeproject.com/Articles/74018/How-to-Parse-and-Convert-a-Delegate-into-an-Expre
目前较好的方法是用Microsoft 的 Dynamic Linq (http://msdn.microsoft.com/en-us/vcsharp/bb894665.aspx)
static void Main(string[] args)
{
string[] exps = new string[]
{
@" ""keyA"" !=""valA""",
@"keyA !=""valA""",
@"(keyA ==""valA"")",
@"keyA ==""val1"" || key2 ==""val2""",
@"key1 ==""val1"" && key2 ==""val2""",
@" key1 !=""val1"" || key2 ==""val2""&& key3 != ""val3""",
@"(key1 ==""val1"" || key2 ==""val2"")&& key3 != ""val3""",
};
string pattern = @"(?[wd_]+)""*s*(?==|!=)s*""*(?[wd_]+)";
foreach (var exp in exps)
{
// Parses to get the parameters. string formattedExp = exp;
var matches = Regex.Matches(exp, pattern);
ParameterExpression[] parameters= new ParameterExpression[matches.Count];
for (int i =0; i < matches.Count; i++)
{
Debug.Write(" key[" + matches[i].Groups["key"].Value);
Debug.Write("] equality[" + matches[i].Groups["equality"].Value);
Debug.Write("] value[" + matches[i].Groups["value"].Value +"]
");
parameters[i]= Expression.Parameter(typeof(string), matches[i].Groups["key"].Value);
// Removing " if it has in keys. if (exp.Contains(string.Format(@"""{0}""", matches[i].Groups["key"].Value)))
{
formattedExp= exp.Replace(string.Format(@"""{0}""", matches[i].Groups["key"].Value), matches[i].Groups["key"].Value);
}
}
var e = System.Linq.Dynamic.DynamicExpression.ParseLambda(parameters, null, formattedExp);
string[] GotValues = new string[matches.Count];
if (GotValues.Length == 2)
{
GotValues[0] = "val1";
GotValues[1] = "val2";
}
if (GotValues.Length == 3)
{
GotValues[0] = "val1";
GotValues[1] = "val2";
GotValues[2] = "val3";
}
var result = e.Compile().DynamicInvoke(GotValues);
Debug.WriteLine("{0} ---> {1}", e.ToString(), result);
}
}
输出如下:
keyA => (keyA != "valA") ---> True
key[keyA] equality[!=] value[valA]
keyA => (keyA != "valA") ---> True
key[keyA] equality[==] value[valA]
keyA => (keyA == "valA") ---> False
key[keyA] equality[==] value[val1]
key[key2] equality[==] value[val2]
(keyA, key2) => ((keyA == "val1") OrElse (key2 == "val2")) ---> True
key[key1] equality[==] value[val1]
key[key2] equality[==] value[val2]
(key1, key2) => ((key1 == "val1") AndAlso (key2 == "val2")) ---> True
key[key1] equality[!=] value[val1]
key[key2] equality[==] value[val2]
key[key3] equality[!=] value[val3]
(key1, key2, key3) => ((key1 != "val1") OrElse ((key2 == "val2") AndAlso (key3 != "val3"))) ---> False
key[key1] equality[==] value[val1]
key[key2] equality[==] value[val2]
key[key3] equality[!=] value[val3]
(key1, key2, key3) => (((key1 == "val1") OrElse (key2 == "val2")) AndAlso (key3 != "val3")) ---> False
参考:
https://stackoverflow.com/questions/821365/how-to-convert-a-string-to-its-equivalent-linq-expression-tree
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