“Property set method not found” error during refle

问题:

I'm trying to reflect over some class properties and set them programaticlly, but it looks like one of my PropertyInfo filters isn't working:

//Get all public or private non-static properties declared in this class (no inherited properties) - that have a getter and setter.
PropertyInfo[] props = this.GetType().GetProperties(BindingFlags.DeclaredOnly | BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.GetProperty | BindingFlags.SetProperty );

I'm getting an error on the line

pi.SetValue(this, valueFromData, null);

Because the property has only a get{} method, no set{} method.

My question is, why wasn't this property filtered out of props? I thought that was the purpose of BindingFlags.SetProperty.

The property not getting filtered out is:

    public String CollTypeDescription
    {
        get { return _CollTypeDescription; }
    }

Note that I want to filter properties that won't work ahead of time, because I'm listing them all at once. I do not want to use pi.GetSetMethod() after the fact to determine whether I can use the setter.

回答1:

From the documentation:

BindingFlags.SetProperty

Specifies that the value of the specified property should be set. For COM properties, specifying this binding flag is equivalent to specifying PutDispProperty and PutRefDispProperty.

BindingFlags.SetProperty and BindingFlags.GetProperty do not filter properties that are missing setters or getters, respectively.

To check if a property can be set, use the CanWrite property.

if (pi.CanWrite)
    pi.SetValue(this, valueFromData, null);

回答2:

Thanks to ken for the information. It looks like the best solution I can get it to filter them out by testing GetSetMethod(true) in a LINQ filter:

// Get all public or private non-static properties declared in this class
// (e.g. excluding inherited properties) that have a getter and setter.
PropertyInfo[] props = this.GetType()
    .GetProperties(BindingFlags.DeclaredOnly | BindingFlags.Instance |
                   BindingFlags.Public | BindingFlags.NonPublic)
    .Where(p => p.GetGetMethod(true) != null && p.GetSetMethod(true) != null)
    .ToArray();

Alternatively, using CanRead and CanWrite:

PropertyInfo[] props = this.GetType()
    .GetProperties(BindingFlags.DeclaredOnly | BindingFlags.Instance |
                   BindingFlags.Public | BindingFlags.NonPublic)
    .Where(p => p.CanRead && p.CanWrite)
    .ToArray();

It's unclear to me whether these different approaches will yield different results for different protection levels of the get/set methods.

回答3:

I understand the GetProperties() method so that it returns every property that has BindingFlags.GetProperty or BindingFlags.SetProperty.
So if you want only properties that have setters you must remove the BindingFlags.GetProperty flag. But I did not tested it so I can be wrong.

My answer got a -1. So it seems that my answer is wrong.