我只是尝试使用Linq.Expression创建与下面相同的表达式:
Expression<Func<Organization, bool>> expression = @org =>
@org.OrganizationFields.Any(a =>
a.CustomField.Name == field.Name &&
values.Contains(a.Value));
在上面的这个例子中,我有一个名为Organization的实体,它有一个名为OrganizationsFields的属性为IEnumerable,我想查找与Any参数表达式匹配的任何匹配项。
我只是使用下面的代码动态生成表达式:
string[] values = filter.GetValuesOrDefault();
ParameterExpression parameter = Expression.Parameter(typeof(T), "org");
Expression organizationFields = Expression.Property(parameter, "OrganizationFields");
MethodInfo any = typeof(Enumerable)
.GetMethods()
.FirstOrDefault(a => a.Name == "Any" && a.GetParameters().Count() == 2)
.MakeGenericMethod(typeof(OrganizationField));
Func<OrganizationField, bool> functionExpression = a =>
a.CustomField.Name == filter.Name && values.Contains(a.Value);
Expression functionParam = Expression.Constant(
functionExpression,
typeof(Func<OrganizationField, bool>));
Expression call = Expression.Call(organizationFields, any, functionParam);
return Expression.Lambda<Func<T, bool>>(call, parameter);
当我调用方法Expression.Call它抛出一个ArgumentExeption
时会出现问题任何人都可以帮助我吗?
此致
答案 0 :(得分:6)
你去吧
var org = Expression.Parameter(typeof(Organization), "org");
Expression<Func<OrganizationField, bool>> predicate =
a => a.CustomField.Name == filter.Name && values.Contains(a.Value);
var body = Expression.Call(typeof(Enumerable), "Any", new[] { typeof(OrganizationField) },
Expression.PropertyOrField(org, "OrganizationFields"), predicate);
var lambda = Expression.Lambda<Func<Organization, bool>>(body, org);
基本部分(包括您的帖子标题)是以下有用Expression.Call
overload
public static MethodCallExpression Call(
Type type,
string methodName,
Type[] typeArguments,
params Expression[] arguments
)
另请注意,predicate
的{{1}}参数必须作为Any
传递给Expression.Call
。