DDWiki/分享/后端/DDD/2、比throw更好的处理方式.md

往往在架构中`throw`随处可见。

```
throw new ArgumentException($"Input {parameterName} was not in required format", parameterName);
```

`Ardalis.GuardClauses`用来解决这个问题。

```
<ItemGroup>
	<PackageReference Include="Ardalis.GuardClauses" Version="3.0.1" />
</ItemGroup>
```

用法

```
    public class Order
    {
        private string _name;
        private int _quantity;
        private long _max;
        private decimal _unitPrice;
        private DateTime _dateCreated;

        public Order(string name, int quantity, long max, decimal unitPrice, DateTime dateCreated)
        {
            _name = Guard.Against.NullOrWhiteSpace(name, nameof(name));
            _quantity = Guard.Against.NegativeOrZero(quantity, nameof(quantity));
            _max = Guard.Against.Zero(max, nameof(max));
            _unitPrice = Guard.Against.Negative(unitPrice, nameof(unitPrice));
            _dateCreated = Guard.Against.OutOfSQLDateRange(dateCreated, nameof(dateCreated));
        }
    }
```

通过`IGuardClause`实现扩展

```
namespace Ardalis.GuardClauses
{
    public static class Extensions
    {
        public static string Foo(this IGuardClause guardClause, string input, string parameterName)
        {
            if(input?.ToLower() == "foo")
            {
                throw new ArgumentException("Should not have been foo", parameterName);
            }
            return input;
        }
    }
}
```

于是

```
_name = Guard.Against.Foo(name, nameof(name));
```