CODEWITHSUNDEEP
.netreflection
MiguelE
MiguelE

Reputation:

Get class property name

I have my winform application gathering data using databinding. Everything looks fine except that I have to link the property with the textedit using a string:

Me.TextEdit4.DataBindings.Add(New System.Windows.Forms.Binding("EditValue", Me.MyClassBindingSource, "MyClassProperty", True))

This works fine but if I change the class' property name, the compiler obviously will not warn me .

I would like to be able to get the property name by reflection but I don't know how to specify the name of the property I want (I only know how to iterate among all the properties of the class)

Any idea?

Upvotes: 11

Views: 7557

Answers (6)

Romain Verdier
Romain Verdier

Reputation: 12971

If you are using C# 3.0, there is a way to get the name of the property dynamically, without hard coded it.

private string GetPropertyName<TValue>(Expression<Func<BindingSourceType, TValue>> propertySelector)
{
    var memberExpression = propertySelector.Body as MemberExpression;
    return memberExpression != null 
           ? memberExpression.Member.Name 
           : string.empty;
}

Where BindingSourceType is the class name of your datasource object instance.

Then, you could use a lambda expression to select the property you want to bind, in a strongly typed manner :

this.textBox.DataBindings.Add(GetPropertyName(o => o.MyClassProperty),
                              this.myDataSourceObject,
                              "Text");

It will allow you to refactor your code safely, without braking all your databinding stuff. But using expression trees is the same as using reflection, in terms of performance.

The previous code is quite ugly and unchecked, but you get the idea.

Upvotes: 8

aku
aku

Reputation: 123966

Here is an example of what I'm talking about:

[AttributeUsage(AttributeTargets.Property)]
class TextProperyAttribute: Attribute
{}

class MyTextBox
{
    [TextPropery]
    public string Text { get; set;}
    public int Foo { get; set;}
    public double Bar { get; set;}
}


static string GetTextProperty(Type type)
{
    foreach (PropertyInfo info in type.GetProperties())
    {
        if (info.GetCustomAttributes(typeof(TextProperyAttribute), true).Length > 0)
        {
            return info.Name;
        }
    }

    return null;
}

...

Type type = typeof (MyTextBox);

string name = GetTextProperty(type);

Console.WriteLine(name); // Prints "Text"

Upvotes: 6

martinsb
martinsb

Reputation: 945

1) Specify the exact property name that you want and keep it that way

2) Write a test involving that property name.

Upvotes: 0

Guvante
Guvante

Reputation: 19203

You can reflect a Type, but you can't reflect its members except by name.

If that were the only property, or you knew for certain the ordering you could find it by index, but generally speaking a string is the safest way to go.

I believe changing the name will cause a run-time exception, but am not 100% certain, in either case that is probably the best possibility.

Assuming no exception occurs automatically, you could add a Debug.Assert that checks to see if the property by that name exists, but again that is run time only.

Upvotes: 0

Konrad Rudolph
Konrad Rudolph

Reputation: 545508

You'll have the same problem using reflection because in order to find the right property in all the type's properties, you'll have to know its name, right?

Upvotes: 0

aku
aku

Reputation: 123966

Ironically reflection expects that you provide property name to get it's info :)

You can create custom attribute, apply it to desired property. Then you will be able to simply get name of the property having this attribute.

Upvotes: 3

Related Questions