Pass property itself to function as parameter in C#

Question

I am looking for a method to pass property itself to a function. Not value of property. Function doesn\'t know in advance which property will be used for sorting. Simplest w

Answer 1

What I found missing from @MatthiasG's answer is how to get property value not just its name.

public static string Meth<T>(Expression<Func<T>> expression)
{
    var name = ((MemberExpression)expression.Body).Member.Name;
    var value = expression.Compile()();
    return string.Format("{0} - {1}", name, value);
}

use:

Meth(() => YourObject.Property);

Answer 2

You can use an lambda expression to pass property information:

void DoSomething<T>(Expression<Func<T>> property)
{
    var propertyInfo = ((MemberExpression)property.Body).Member as PropertyInfo;
    if (propertyInfo == null)
    {
        throw new ArgumentException("The lambda expression 'property' should point to a valid Property");
    }
}

Usage:

DoSomething(() => this.MyProperty);

Answer 3

Just to add from the answers above. You can also do a simple flag for the order direction.

public class Processor
{
    public List<SortableItem> SortableItems { get; set; }

    public Processor()
    {
        SortableItems = new List<SortableItem>();
        SortableItems.Add(new SortableItem { PropA = "b" });
        SortableItems.Add(new SortableItem { PropA = "a" });
        SortableItems.Add(new SortableItem { PropA = "c" });
    }

    public void SortItems(Func<SortableItem, IComparable> keySelector, bool isAscending)
    {
        if(isAscending)
            SortableItems = SortableItems.OrderBy(keySelector).ToList();
        else
            SortableItems = SortableItems.OrderByDescending(keySelector).ToList();
    }
}

Answer 4

I would like to give a simple, easy to understand answer.

Function's parameter is this: System.Func<class, type of the property>

And we pass the Property like this: Function(x => x.Property);

Here is the code:

class HDNData
{
    private int m_myInt;
    
    public int MyInt
    {
        get { return m_myInt; }
    }
    
    public void ChangeHDNData()
    {
        if (m_myInt == 0)
            m_myInt = 69;
        else
            m_myInt = 0;
    }
}

static class HDNTest
{
    private static HDNData m_data = new HDNData();
    
    public static void ChangeHDNData()
    {
        m_data.ChangeHDNData();
    }
    
    public static void HDNPrint(System.Func<HDNData, int> dataProperty)
    {
        Console.WriteLine(dataProperty(m_data));//Print to console the dataProperty (type int) of m_data
    }
}

//******Usage******
HDNTest.ChangeHDNData();
//This is what you want: Pass property itself (which is MyInt) to function as parameter in C#
HDNTest.HDNPrint(x => x.MyInt);

Answer 5

Why don't you use Linq for this? Like:

vehicles.OrderBy(v => v.maxSpeed).ToList();

Answer 6

Great solution over here...

Passing properties by reference in C#

void GetString<T>(string input, T target, Expression<Func<T, string>> outExpr)
{
    if (!string.IsNullOrEmpty(input))
    {
        var expr = (MemberExpression) outExpr.Body;
        var prop = (PropertyInfo) expr.Member;
        prop.SetValue(target, input, null);
    }
}

void Main()
{
    var person = new Person();
    GetString("test", person, x => x.Name);
    Debug.Assert(person.Name == "test");
}