如何检查对象的所有属性是否为空或为空？

Question

I have an object lets call it ObjectA

and that object has 10 properties and those are all strings.

 var myObject = new {Property1="",Property2="",Property3="",Property4="",...}

is there anyway to check to see whether all these properties are null or empty?

So any built-in method that would return true or false?

If any single of them is not null or empty then the return would be false. If all of them are empty it should return true.

The idea is I do not want to write 10 if statement to control if those properties are empty or null.

Thanks

Answer 1

You can do it using Reflection

bool IsAnyNullOrEmpty(object myObject)
{
    foreach(PropertyInfo pi in myObject.GetType().GetProperties())
    {
        if(pi.PropertyType == typeof(string))
        {
            string value = (string)pi.GetValue(myObject);
            if(string.IsNullOrEmpty(value))
            {
                return true;
            }
        }
    }
    return false;
}

Matthew Watson suggested an alternative using LINQ :

return myObject.GetType().GetProperties()
    .Where(pi => pi.PropertyType == typeof(string))
    .Select(pi => (string)pi.GetValue(myObject))
    .Any(value => string.IsNullOrEmpty(value));

Answer 2

I suppose you want to make sure that all properties are filled in.

A better option is probably by putting this validation in the constructor of your class and throw exceptions if validation fails. That way you cannot create a class that is invalid; catch exceptions and handle them accordingly.

Fluent validation is a nice framework ( http://fluentvalidation.codeplex.com ) for doing the validation. Example:

public class CustomerValidator: AbstractValidator<Customer> 
{
    public CustomerValidator()
    {
        RuleFor(customer => customer.Property1).NotNull();
        RuleFor(customer => customer.Property2).NotNull();
        RuleFor(customer => customer.Property3).NotNull();
    }
}

public class Customer
{
    public Customer(string property1, string property2, string property3)
    {
         Property1  = property1;
         Property2  = property2;
         Property3  = property3;
         new CustomerValidator().ValidateAndThrow();
    }

    public string Property1 {get; set;}
    public string Property2 {get; set;}
    public string Property3 {get; set;}
}

Usage:

 try
 {
     var customer = new Customer("string1", "string", null);
     // logic here
 } catch (ValidationException ex)
 {
     // A validation error occured
 }

PS - Using reflection for this kind of thing just makes your code harder to read. Using validation as shown above makes it explicitly clear what your rules are; and you can easily extend them with other rules.

Answer 3

The following code returns if any property is not null.

  return myObject.GetType()
                 .GetProperties() //get all properties on object
                 .Select(pi => pi.GetValue(myObject)) //get value for the property
                 .Any(value => value != null); // Check if one of the values is not null, if so it returns true.

Answer 4

Here you go

var instOfA = new ObjectA();
bool isAnyPropEmpty = instOfA.GetType().GetProperties()
     .Where(p => p.GetValue(instOfA) is string) // selecting only string props
     .Any(p => string.IsNullOrWhiteSpace((p.GetValue(instOfA) as string)));

and here's the class

class ObjectA
{
    public string A { get; set; }
    public string B { get; set; }
}

Answer 5

A slightly different way of expressing the linq to see if all string properties of an object are non null and non empty:

public static bool AllStringPropertyValuesAreNonEmpty(object myObject)
{
    var allStringPropertyValues = 
        from   property in myObject.GetType().GetProperties()
        where  property.PropertyType == typeof(string) && property.CanRead
        select (string) property.GetValue(myObject);

    return allStringPropertyValues.All(value => !string.IsNullOrEmpty(value));
}

Answer 6

Note if you've got a data structural hierarchy and you want to test everything in that hierarchy, then you can use a recursive method. Here's a quick example:

static bool AnyNullOrEmpty(object obj) {
  return obj == null
      || obj.ToString() == ""
      || obj.GetType().GetProperties().Any(prop => AnyNullOrEmpty(prop.GetValue(obj)));
}

Answer 7

仅检查所有属性是否为空：

bool allPropertiesNull = !myObject.GetType().GetProperties().Any(prop => prop == null);

Answer 8

you can use reflection and extension methods to do this.

using System.Reflection;
public static class ExtensionMethods
{
    public static bool StringPropertiesEmpty(this object value)
    {
        foreach (PropertyInfo objProp in value.GetType().GetProperties())
        {
            if (objProp.CanRead)
            {
                object val = objProp.GetValue(value, null);
                if (val.GetType() == typeof(string))
                {
                    if (val == "" || val == null)
                    {
                        return true;
                    }
                }
            }
        }
        return false;
    }
}

then use it on any object with string properties

test obj = new test();
if (obj.StringPropertiesEmpty() == true)
{
    // some of these string properties are empty or null
}

Answer 9

No, I don't think there is a method to do exactly that.

You'd be best writing a simple method that takes your object and returns true or false.

Alternatively, if the properties are all the same, and you just want to parse through them and find a single null or empty, perhaps some sort of collection of strings would work for you?

Answer 10

You can try the following query :

if the object is "referenceKey" (where few properties may be null )

referenceKey.GetType().GetProperties().Where(x => x.GetValue(referenceKey) == null)

I need to count the properties where the value is set to not Null, so I have used the following query :

 var countProvidedReferenceKeys = referenceKey.GetType().GetProperties().Where(x => x.GetValue(referenceKey) != null).Count();