Adding validations on class fields in WCF

Question

I have a class Customers. I want to put some validations on it. e.g. CustGuidId is not Guid.Empty, CustName is NOT NULL (Required).

public class Customer
{
    public int CustId;
    public string CustName;
    public Guid CustGuid;
    public Guid[] OrderGuids;
}

I have such collection of customers. So I have ended up adding code like this, which makes it look ugly.

public class BatchError
{
    public int Index;
    public string ErrorCode;
    public string ErrorMessage;
}


public void GenerateValidationErrors(List<Customer> customers, out List<BatchError> batchErrors)
    {
        int rowNum = 0;
        batchErrors = new List<BatchError>(customers.Count);

        foreach (var customer in customers)
        {
            rowNum ++;
            Guid customerGuidParsed;
            if(!Guid.TryParse(customer.CustGuid.ToString(), out customerGuidParsed))
            {
                batchErrors.Add(new BatchError { Index = rowNum, ErrorCode = "CustomerGuidcannotBeNull", ErrorMessage = "Customer guid cannot be null." });
            }
            if (string.IsNullOrEmpty(customer.CustName))
            {
                batchErrors.Add(new BatchError { Index = rowNum, ErrorCode = "CustomerNamecannotBeEmpty", ErrorMessage = "Customer Name cannot be empty." });
            }
        }
    }

Can we write separate validator classes, like GuidValidator, StringValidator. and Create array of delegates & chain their invokes ?

(Customer c) => new GuidValidator(c.CustGuid.toString()),
(Customer c) => new StringValidator(c.CustName.toString())

But what design pattern would be best suitable for this scenario?

Is there any other way to add validations in WCF?

Pranav Singh · Accepted Answer · 2014-06-16 05:39:46Z

There are many ways to do the validation. I prefer to validate DataContract itself before any action. It can also be done in many like :

DatamemberAttribute has many properties. One of them is IsRequired,it controls the minOccurs attribute for the schema element. The default value is false. You can use it like:

[DataContract(Name ="Place", Namespace ="")] public class DataContractExample { [DataMember(IsRequired=true)] public string DataMemberExample; }

For more information refer: DataMemberAttribute Class on MSDN.

Easiest way is to validate property like:

[DataContract] public class Customer { [DataMember] public string CustName { get { return this._custName; } set { if(string.IsNullOrEmpty(value)) throw new MyValidationException(); else this._custName=value; } } }
Another way can be to use Microsoft Enterprise Library. In order to enable validation of the properties of a request message, you only need to add a [ValidationBehavior] attribute to your service interface, just next (or before) the [ServiceContract], and a [FaultContract(typeof(ValidationFault))] on the method declaration. The ValidationBehaviorAttribute and ValidationFault classes are defined in the Microsoft.Practices.EnterpriseLibrary.Validation.Integration.WCF assembly and are part of the Validation Application Block of the Enterprise Library 4.1, more specifically, of the WCF integration module. See full implementation in detail at: http://weblogs.asp.net/ricardoperes/validation-of-wcf-requests-with-the-enterprise-library-validation-block
Finally one more solution cane be to use WCF Data Annotations from http://wcfdataannotations.codeplex.com/. Using this you can use validations like:
```
[DataMember]
[Required]
[StringLength(500, MinimumLength = 5)]
public string Description{ get; set; }
```

Choose which ever suite your requirements. Cheers.

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