Suppose I have decimal property for an entity meta data for wcf ria service:

```
 public Nullable<decimal> Amount { get; set; }

```

I want to the input for this field is something like 0.00, means user must input 2 digitals after decimal dot. If there is nothing, .00 must be there. So, 123.00, 12.23 is file. But 12 or 3345 is not right. 

Then I want to put regular expression as validation attribute on this property in meta data class. 
How can I do it?
Any other solution?

Thanks for answer, guys. Here is the testing:

```
 [RegularExpression("^\\d*\\.\\d{2}$", ErrorMessage = "Put the right number for amount")]
 public Nullable<decimal> Amount { get; set; }

```

This is not working. all 123, 123., 123.00 are acceptable.

Above solution only working for string, like this:

```
 [RegularExpression("^\\d*\\.\\d{2}$", ErrorMessage = "Put the right number for amount")]
 public string Amount { get; set; }

```

How to make it working for Decimal?