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Getting a property description attribute

Existing code (simplified)

I have this function

public static string[] GetFieldNames<T>(IEnumerable<T> items)
  where T : class
{
  var properties = typeof(T).GetProperties().Where(p => SystemTypes.Contains(p.PropertyType)); // Only get System types

  return properties.Select(p => p.Name).ToArray();
}

So if I have this class

class MyClass {
  public string Name { get; set; }

  [Description("The value")]
  public int Value { get; set; }
}

I may have a code like this

List<MyClass> items = ...; // Populate items somehow
string[] fieldNames = GetFieldNames(items); // This returns ["Name", "Value"]

This works great.

Problem

I need to get the description (if it exists), so it GetFieldNames(items)

returns["Name", "The value"]

How do I change the function GetFieldNames()

to read the Description attribute if it exists?
(Note that this function has been simplified, the real function is much more complex, so please don't change the logic)

+3


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4 answers


This should work for you:



return properties.Select(p => 
    Attribute.IsDefined(p, typeof(DescriptionAttribute)) ? 
        (Attribute.GetCustomAttribute(p, typeof(DescriptionAttribute)) as DescriptionAttribute).Description:
        p.Name
    ).ToArray();
+3


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NOTE: just add using System.Reflection

as GetCustomAttribute

this is an extension method in .Net 4.5

public static Tuple<string,string>[] GetFieldNames<T>(IEnumerable<T> items) where T : class
{
    var result =
        typeof (T).GetProperties()
            .Where(p => SystemTypes.Contains(p.PropertyType) &&p.GetCustomAttribute<DescriptionAttribute>() != null)
            .Select(
                p =>
                    new Tuple<string, string>(p.Name,
                        p.GetCustomAttribute<DescriptionAttribute>().Description));

    return result.ToArray();
}


for an earlier version of the .NET Framework, we can use this extension method:

public static class Extension
{
    public static T GetCustomAttribute<T>(this System.Reflection.MemberInfo mi) where T : Attribute
    {
        return mi.GetCustomAttributes(typeof (T),true).FirstOrDefault() as T;
    }
}
+3


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use the GetCustomAttributes method

    static void attributecheck()
    {
        var props = typeof(Product).GetProperties();
        foreach (var propertyInfo in props)
        {
            var att = propertyInfo.GetCustomAttributes(typeof(DescriptionAttribute), true);
            if (att.Length >0)
            {
            }
        }
    }
0


source


This is a generic function that you can use if the attribute fieldName

has an attribute description

, it returns a value, otherwise it returns null

.

public string GetDescription<T>(string fieldName)
{
    string result;
    FieldInfo fi = typeof(T).GetField(fieldName.ToString());
    if (fi != null)
    {
        try
        {
            object[] descriptionAttrs = fi.GetCustomAttributes(typeof(DescriptionAttribute), false);
            DescriptionAttribute description = (DescriptionAttribute)descriptionAttrs[0];
            result = (description.Description);
        }
        catch
        {
            result = null;
        }
    }
    else
    {
        result = null;
    }

    return result;
}

Example:

class MyClass {
  public string Name { get; set; }

  [Description("The age description")]
  public int Age { get; set; }
}

string ageDescription = GetDescription<MyClass>("age");
console.log(ageDescription) // OUTPUT: The age description
0


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