我正在尝试使用c＃建立动态过滤机制。
我有一个具有名称，姓氏，出生日期等属性的用户类，还有UserInformations列表，它是UserInformation对象的列表。 UserInformation对象具有属性Id，名称和值。 用户列表中的userList。
我创建了一个使用https://querybuilder.js.org/demo.html
来创建过滤器页面的UI它会生成类似
的过滤器{
"condition": "AND",
"rules": [
{
"id": "name",
"field": "name",
"type": "string",
"input": "text",
"operator": "equal",
"value": "huseyin"
},
{
"condition": "OR",
"rules": [
{
"id": "surname",
"field": "surname",
"type": "string",
"input": "text",
"operator": "equal",
"value": "34"
},
{
"id": "ix_2_Weight",
"field": "ix_2_Weight",
"type": "integer",
"input": "select",
"operator": "equal",
"value": 50
}
]
}
],
"valid": true
}
我对具有User属性的过滤器没有任何问题。但是，我试图过滤UserInformations数组中的信息。 我正在拆分字段名称（如果其名称以ix开头）并获取用户信息的ID。但我找不到如何比较其价值。 如果它是静态linq，应该像
users.Where(u=>u.Informations.FirstOrDefault(i=>i.id==2/*id of information in filter*/)?.Value=="something"))
使用以下代码调用过滤器
private async Task<List<User>> FilterUsers(FilterRule rule, List<UserFilterDto> users = null)
{
List<User> list = users ?? await GetUsersForFilter();
var tempList = list.BuildQuery(rule).ToList();
return tempList;
}
动态查询部分如下。
public static IQueryable<User> BuildQuery(this IQueryable<User> queryable, FilterRule filterRule, out string parsedQuery, bool useIndexedProperty = false, string indexedPropertyName = null)
{
if (filterRule == null)
{
parsedQuery = "";
return queryable;
}
var pe = Expression.Parameter(typeof(UserDetailedDto), "item");
var expressionTree = BuildExpressionTree(pe, filterRule, useIndexedProperty, indexedPropertyName);
if (expressionTree == null)
{
parsedQuery = "";
return queryable;
}
parsedQuery = expressionTree.ToString();
var whereCallExpression = Expression.Call(
typeof(Queryable),
"Where",
new[] { queryable.ElementType },
queryable.Expression,
Expression.Lambda<Func<UserDetailedDto, bool>>(expressionTree, pe));
var filteredResults = queryable.Provider.CreateQuery<UserDetailedDto>(whereCallExpression);
return filteredResults;
}
public static IQueryable<User> BuildQuery(this IQueryable<User> queryable, FilterRule filterRule, out string parsedQuery, bool useIndexedProperty = false, string indexedPropertyName = null)
{
if (filterRule == null)
{
parsedQuery = "";
return queryable;
}
var pe = Expression.Parameter(typeof(UserDetailedDto), "item");
var expressionTree = BuildExpressionTree(pe, filterRule, useIndexedProperty, indexedPropertyName);
if (expressionTree == null)
{
parsedQuery = "";
return queryable;
}
parsedQuery = expressionTree.ToString();
var whereCallExpression = Expression.Call(
typeof(Queryable),
"Where",
new[] { queryable.ElementType },
queryable.Expression,
Expression.Lambda<Func<UserDetailedDto, bool>>(expressionTree, pe));
var filteredResults = queryable.Provider.CreateQuery<UserDetailedDto>(whereCallExpression);
return filteredResults;
}
private static Expression BuildExpressionTree(ParameterExpression pe, FilterRule rule, bool useIndexedProperty = false, string indexedPropertyName = null)
{
if (rule.Rules != null && rule.Rules.Any())
{
var expressions =
rule.Rules.Select(childRule => BuildExpressionTree(pe, childRule, useIndexedProperty, indexedPropertyName))
.Where(expression => expression != null)
.ToList();
var expressionTree = expressions.First();
var counter = 1;
while (counter < expressions.Count)
{
expressionTree = rule.Condition.ToLower() == "or"
? Expression.Or(expressionTree, expressions[counter])
: Expression.And(expressionTree, expressions[counter]);
counter++;
}
return expressionTree;
}
if (rule.Field != null)
{
Type type;
switch (rule.Type)
{
case "integer":
type = typeof(int);
break;
case "long":
type = typeof(long);
break;
case "double":
type = typeof(double);
break;
case "string":
type = typeof(string);
break;
case "date":
case "datetime":
type = typeof(DateTime);
break;
case "boolean":
type = typeof(bool);
break;
default:
throw new Exception($"Unexpected data type {rule.Type}");
}
Expression propertyExp = null;
if (rule.Field.StartsWith("ix"))
{
long informationId =long.Parse(rule.Field.Split("_")[1]);
????
????
} else if (useIndexedProperty)
{
propertyExp = Expression.Property(pe, indexedPropertyName, Expression.Constant(rule.Field));
}
else
{
propertyExp = Expression.Property(pe, rule.Field);
}
Expression expression;
if (propertyExp.Type.Name.Contains("ICollection") || propertyExp.Type.Name.Contains("List"))
{
// Rule Field is a Collection
expression = BuildCollectionExpression(pe, rule);
}
else
{
switch (rule.Operator.ToLower())
{
case "in":
expression = In(type, rule.Value, propertyExp);
break;
case "not_in":
expression = NotIn(type, rule.Value, propertyExp);
break;
case "equal":
expression = Equals(type, rule.Value, propertyExp);
break;
case "not_equal":
expression = NotEquals(type, rule.Value, propertyExp);
break;
case "between":
expression = Between(type, rule.Value, propertyExp);
break;
case "not_between":
expression = NotBetween(type, rule.Value, propertyExp);
break;
case "less":
expression = LessThan(type, rule.Value, propertyExp);
break;
case "less_or_equal":
expression = LessThanOrEqual(type, rule.Value, propertyExp);
break;
case "greater":
expression = GreaterThan(type, rule.Value, propertyExp);
break;
case "greater_or_equal":
expression = GreaterThanOrEqual(type, rule.Value, propertyExp);
break;
case "begins_with":
expression = BeginsWith(type, rule.Value, propertyExp);
break;
case "not_begins_with":
expression = NotBeginsWith(type, rule.Value, propertyExp);
break;
case "contains":
expression = Contains(type, rule.Value, propertyExp);
break;
case "not_contains":
expression = NotContains(type, rule.Value, propertyExp);
break;
case "ends_with":
expression = EndsWith(type, rule.Value, propertyExp);
break;
case "not_ends_with":
expression = NotEndsWith(type, rule.Value, propertyExp);
break;
case "is_empty":
expression = IsEmpty(propertyExp);
break;
case "is_not_empty":
expression = IsNotEmpty(propertyExp);
break;
case "is_null":
expression = IsNull(propertyExp);
break;
case "is_not_null":
expression = IsNotNull(propertyExp);
break;
default:
throw new Exception($"Unknown expression operator: {rule.Operator}");
}
}
return expression;
}
return null;
}
答案 0 :(得分：2)
如果它是静态LINQ，应该就像
u => u.Informations.FirstOrDefault(i => i.id == 2)?.Value == "something"))
运算符?.在表达式树中不受支持，因此最好改成这样的东西：
u => u.Informations.Any(i => i.id == 2 && i.Value == "something"))
为此，请使用另一种方法提取原始表达式构建：
private static Expression BuildCondition(FilterRule rule, Expression propertyExp)
{
Type type;
switch (rule.Type)
{
case "integer":
type = typeof(int);
break;
case "long":
type = typeof(long);
break;
case "double":
type = typeof(double);
break;
case "string":
type = typeof(string);
break;
case "date":
case "datetime":
type = typeof(DateTime);
break;
case "boolean":
type = typeof(bool);
break;
default:
throw new Exception($"Unexpected data type {rule.Type}");
}
Expression expression;
switch (rule.Operator.ToLower())
{
case "in":
expression = In(type, rule.Value, propertyExp);
break;
case "not_in":
expression = NotIn(type, rule.Value, propertyExp);
break;
case "equal":
expression = Equals(type, rule.Value, propertyExp);
break;
case "not_equal":
expression = NotEquals(type, rule.Value, propertyExp);
break;
case "between":
expression = Between(type, rule.Value, propertyExp);
break;
case "not_between":
expression = NotBetween(type, rule.Value, propertyExp);
break;
case "less":
expression = LessThan(type, rule.Value, propertyExp);
break;
case "less_or_equal":
expression = LessThanOrEqual(type, rule.Value, propertyExp);
break;
case "greater":
expression = GreaterThan(type, rule.Value, propertyExp);
break;
case "greater_or_equal":
expression = GreaterThanOrEqual(type, rule.Value, propertyExp);
break;
case "begins_with":
expression = BeginsWith(type, rule.Value, propertyExp);
break;
case "not_begins_with":
expression = NotBeginsWith(type, rule.Value, propertyExp);
break;
case "contains":
expression = Contains(type, rule.Value, propertyExp);
break;
case "not_contains":
expression = NotContains(type, rule.Value, propertyExp);
break;
case "ends_with":
expression = EndsWith(type, rule.Value, propertyExp);
break;
case "not_ends_with":
expression = NotEndsWith(type, rule.Value, propertyExp);
break;
case "is_empty":
expression = IsEmpty(propertyExp);
break;
case "is_not_empty":
expression = IsNotEmpty(propertyExp);
break;
case "is_null":
expression = IsNull(propertyExp);
break;
case "is_not_null":
expression = IsNotNull(propertyExp);
break;
default:
throw new Exception($"Unknown expression operator: {rule.Operator}");
}
return expression;
}
在当前分支内部将其用于直接成员，并将以下内容用于“索引”分支：
if (rule.Field.StartsWith("ix_"))
{
var tokens = rule.Field.Split("_");
var infoParameter = Expression.Parameter(typeof(UserInformation), "i");
var infoCondition = Expression.AndAlso(
Expression.Equal(
Expression.Property(infoParameter, nameof(UserInformation.Id)),
Expression.Constant(long.Parse(tokens[1]))),
BuildCondition(rule, Expression.Property(infoParameter, tokens[2])));
return Expression.Call(
typeof(Enumerable), nameof(Enumerable.Any), new[] { infoParameter.Type },
Expression.Property(pe, nameof(User.Informations)),
Expression.Lambda(infoCondition, infoParameter));
}
请注意，C＃逻辑&&和||运算符由Expression.AndAlso和Expression.OrElse表示。