WF4活动验证:RequiredArgument,OverloadGroup及Constraints

1.RequiredArgument 和OverloadGroup 属性

OverloadGroup可以把活动中的参数和属性分成不同的组，每组作为一个整体。每组的属性必须同时指定。方式如下：

[RequiredArgument]
[OverloadGroup("G1")]
public InArgument<int> Num{ get; set; }

也可以在XAML中使用，如下：

<x:Property Name="Operand1" Type="InArgument(x:Int32)">
    <x:Property.Attributes>
        <RequiredArgumentAttribute />
    </x:Property.Attributes>
</x:Property>

例假如有一个请假单活动，我们要求申请者，部分必须同时填写，请假的开始时间应小于结束时间，自定义活动如下：

public sealed class LeaveForm:CodeActivity
    {
        [RequiredArgument]
        [OverloadGroup("G1")]
        public InArgument<string> ApplyName { get; set; }

        [RequiredArgument]
        [OverloadGroup("G1")]
        public InArgument<string> ApplyDept { get; set; }

        public DateTime StartTime { get; set; }
        public DateTime EndTime { get; set; }

        protected override void CacheMetadata(CodeActivityMetadata metadata)
        {
            base.CacheMetadata(metadata);
            if(StartTime>EndTime)
            {
                metadata.AddValidationError("开始时间应小于结束时间");
            }
        }
        protected override void Execute(CodeActivityContext context)
        {            
        }
    }

如果没有验证通过设计器会有相应的提示信息，如下图：

2.Constraints

WF4还提供了Constraints，Constraint也是一个活动，他包含了验证的逻辑。我们可以将Constraint加入到活动的Constraints属性中进行验证。如下：

public sealed class CaryActivity : CodeActivity
{
    public CaryActivity()
    {
        base.Constraints.Add(CheckPickBranch());
    }
}

也可以使用ValidationSettings实例的AdditionalConstraints属性。下面举例：

先来定义两个约束：

class CaryConstraints
    {        
        public static Constraint CheckThenOrElse() 
        {
            DelegateInArgument<If> element = new DelegateInArgument<If>();

            return new Constraint<If>
            {
                Body = new ActivityAction<If, ValidationContext>
                {
                    Argument1 = element,
                    Handler = new AssertValidation
                    {                        
                        Assertion = new InArgument<bool>(env => (element.Get(env).Then != null)
                                                         || (element.Get(env).Else != null)),
                        Message = new InArgument<string>("'If' 活动应该有Then或Else"),
                    }
                }
            };
        }

        public static Constraint CheckPickBranch() 
        {
            DelegateInArgument<Pick> element = new DelegateInArgument<Pick>();

            return new Constraint<Pick>
            {
                Body = new ActivityAction<Pick, ValidationContext>
                {
                    Argument1 = element,
                    Handler = new AssertValidation
                    {
                        IsWarning = true,
                        Assertion = new InArgument<bool>(env => (element.Get(env).Branches.Count == 0)
                                                         || (element.Get(env).Branches.Count > 1)),
                        Message = new InArgument<string>("这个Pick活动只有一个分支"),
                       
                    }
                }
            };
        }
    }

工作流如下：

调用如下：

static void Main()
        {            
            ValidationSettings validationSettings = new ValidationSettings
            {                
                AdditionalConstraints =
                    {                             
                        {typeof(If), new List<Constraint> {CaryConstraints.CheckThenOrElse()}}, 
                        {typeof(Pick), new List<Constraint> {CaryConstraints.CheckPickBranch()}}
                    }
            };
            ValidationResults results = ActivityValidationServices.Validate(new CaryAL.Activity1(), validationSettings);
            if (results.Errors.Count == 0 && results.Warnings.Count == 0)
            {
                Console.WriteLine("No warnings or errors");
            }
            else
            {                
                foreach (ValidationError error in results.Errors)
                {
                    Console.WriteLine("Error: " + error.Message);
                }
                foreach (ValidationError warning in results.Warnings)
                {
                    Console.WriteLine("Warning: " + warning.Message);
                }
            }          
        }

结果如下：

Error: The private implementation of activity '1: Activity1' has the following validation error: 
'If' 活动应该有Then或Else
Warning: The private implementation of activity '1: Activity1' has the following validation error: 
这个Pick活动只有一个分支

请按任意键继续. . .