How do I sort a generic list based on a custom attribute?
I am workin开发者_StackOverflow社区g in c#.NEt 2.0. I have a class, let's say X with many properties. Each properties has a custom attribute, an interger, which I planned to use to specify its order int he final array.
Using reflection I read through all of the properties and group the values and place them into a generic list of properties. This works and I can grab the values. But the plan was SORT the list, based on the custom attribute placed on each property, and finally read out the propery values, already ordered, into a string.
Lets say you had the following attribute definition
public class SortAttribute : Attribute {
public int Order { get; set; }
public SortAttribute(int order) { Order = order; }
}
You could use the following code to pull out the properties on a type in sorted order. Assuming of course they all have this attribute
public IEnumerable<object> GetPropertiesSorted(object obj) {
Type type = obj.GetType();
List<KeyValuePair<object,int>> list = new List<KeyValuePair<object,int>>();
foreach ( PropertyInfo info in type.GetProperties()) {
object value = info.GetValue(obj,null);
SortAttribute sort = (SortAttribute)Attribute.GetCustomAttribute(x, typeof(SortAttribute), false);
list.Add(new KeyValuePair<object,int>(value,sort.Order));
}
list.Sort(delegate (KeyValuePair<object,int> left, KeyValuePair<object,int> right) { left.Value.CompareTo right.Value; });
List<object> retList = new List<object>();
foreach ( var item in list ) {
retList.Add(item.Key);
}
return retList;
}
LINQ Style Solution
public IEnumerable<string> GetPropertiesSorted(object obj) {
var type = obj.GetType();
return type
.GetProperties()
.Select(x => new {
Value = x.GetValue(obj,null),
Attribute = (SortAttribute)Attribute.GetCustomAttribute(x, typeof(SortAttribute), false) })
.OrderBy(x => x.Attribute.Order)
.Select(x => x.Value)
.Cast<string>();
}
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