MinValue & MaxValue attribute for properties

Question

Is it possible to make attribute which can limit minimum or maximum value of numbers.

Example:

[MinValue(1), MaxValue(50)]
public int Size { get; set; }

and when i do Size = -3; value of Size must be 1.

I searched in Google and can't find single example about this behavior, maybe because it is not possible to make?

I'm gonna use these attributes in property grid therefore having automatic validation can be handy.

Currently I workaround like this to limit minimum value:

    private int size;

    [DefaultValue(8)]
    public int Size
    {
        get
        {
            return size;
        }
        set
        {
            size = Math.Max(value, 1);
        }
    }

So this acts like MinValue(1)

Answer 1

Although it is possible to create a custom attribute, attributes are just metadata for the member they annotate, and cannot change its behavior.

So, you won't get the behavior you want with a plain attribute. You need something to process the attributes in order to enact the desired behavior.

Take a look at TypeConverters for a possibility.

Answer 2

Yes, it is possible. Read about custom attributes at MSDN.

And by the way, there is already a solution you can use. It is the RangeAttribute which lets you specify the numeric range constraints for the value of a data field. Read more about it on MSDN.