只允许在特定类型上使用自定义属性

基本上不能。你可以把它限制在struct vs class vs interface，就是这样。另外:你不能添加属性到代码之外的类型(除了通过TypeDescriptor，这是不一样的)。

您可以运行这个单元测试来检查它。

首先，声明验证属性PropertyType:

  [AttributeUsage(AttributeTargets.Class)]
    // [JetBrains.Annotations.BaseTypeRequired(typeof(Attribute))] uncomment if you use JetBrains.Annotations
    public class PropertyTypeAttribute : Attribute
    {
        public Type[] Types { get; private set; }
        public PropertyTypeAttribute(params Type[] types)
        {
            Types = types;
        }
    }

创建单元测试:

 [TestClass]
    public class TestPropertyType 
    {
        public static Type GetNullableUnderlying(Type nullableType)
        {
            return Nullable.GetUnderlyingType(nullableType) ?? nullableType;
        }
        [TestMethod]
        public void Test_PropertyType()
        {
            var allTypes = AppDomain.CurrentDomain.GetAssemblies().SelectMany(a => a.GetTypes());
            var allPropertyInfos = allTypes.SelectMany(a => a.GetProperties()).ToArray();
            foreach (var propertyInfo in allPropertyInfos)
            {
                var propertyType = GetNullableUnderlying(propertyInfo.PropertyType);
                foreach (var attribute in propertyInfo.GetCustomAttributes(true))
                {
                    var attributes = attribute.GetType().GetCustomAttributes(true).OfType<PropertyTypeAttribute>();
                    foreach (var propertyTypeAttr in attributes)
                        if (!propertyTypeAttr.Types.Contains(propertyType))
                            throw new Exception(string.Format(
                                "Property '{0}.{1}' has invalid type: '{2}'. Allowed types for attribute '{3}': {4}",
                                propertyInfo.DeclaringType,
                                propertyInfo.Name,
                                propertyInfo.PropertyType,
                                attribute.GetType(),
                                string.Join(",", propertyTypeAttr.Types.Select(x => "'" + x.ToString() + "'"))));
                }
            }
        }
    }

您的属性，例如，只允许十进制属性类型:

 [AttributeUsage(AttributeTargets.Property)]
    [PropertyType(typeof(decimal))]
    public class PriceAttribute : Attribute
    {
    }

示例模型:

public class TestModel  
{
    [Price]
    public decimal Price1 { get; set; } // ok
    [Price]
    public double Price2 { get; set; } // error
}

如果将属性放置在非List of string的属性/字段上，下面的代码将返回一个错误。

if (!(value is List<string> list))行可能是c# 6或c# 7的特性。

[AttributeUsage(AttributeTargets.Property |
                AttributeTargets.Field, AllowMultiple = false)]
public sealed class RequiredStringListAttribute : ValidationAttribute
{
    protected override ValidationResult IsValid(object value, ValidationContext context)
    {
        if (!(value is List<string> list))
            return new ValidationResult($"The required attrribute must be of type List<string>");
        bool valid = false;
        foreach (var item in list)
        {
            if (!string.IsNullOrWhiteSpace(item))
                valid = true;
        }
        return valid
            ? ValidationResult.Success
            : new ValidationResult($"This field is required"); ;
    }
}

您可以自己编写代码来强制正确使用您的属性类，但这是您所能做的。

我是这样做的:

[AttributeUsage(AttributeTargets.Property)]
public class SomeValidationAttribute : ValidationAttribute
{
    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        if (value is not string stringToValidate)
        {
            throw new AttributeValueIsNotStringException(validationContext.DisplayName, validationContext.ObjectType.Name);
        }
        // validationContext.DisplayName is name of property, where validation attribut was used.
        // validationContext.ObjectType.Name is name of class, in which the property is placed to instantly identify, where is the error.
        
        //Some validation here.
        return ValidationResult.Success;
    }
}

和例外看起来像这样:

public class AttributeValueIsNotStringException : Exception
{
    public AttributeValueIsNotStringException(string propertyName, string className) : base(CreateMessage(propertyName, className))
    {
    }
    private static string CreateMessage(string propertyName, string className)
    {
        return $"Validation attribute cannot be used for property: '"{propertyName}'" in class: '"{className}'" because it's type is not string. Use it only for string properties.";
    }
}