我有一个属性，想从资源文件中加载文本到该属性中。
[IntegerValidation(1, 70, ErrorMessage = Data.Messages.Speed)]
private int i_Speed;
但我一直收到以下错误信息：
"属性参数必须是常量表达式、typeof 表达式或数组创建表达式的属性参数类型"
如果我添加一个字符串而不是Data.Messages.Text，它就可以完美地工作了，例如：
[IntegerValidation(1, 70, ErrorMessage = "Invalid max speed")]
有什么想法吗？
这是我的解决方案。我已经像microsoft在DataAnnotations中所做的那样，添加了resourceName和resourceType属性到attribute中。
public class CustomAttribute : Attribute
{
public CustomAttribute(Type resourceType, string resourceName)
{
Message = ResourceHelper.GetResourceLookup(resourceType, resourceName);
}
public string Message { get; set; }
}
public class ResourceHelper
{
public static string GetResourceLookup(Type resourceType, string resourceName)
{
if ((resourceType != null) && (resourceName != null))
{
PropertyInfo property = resourceType.GetProperty(resourceName, BindingFlags.Public | BindingFlags.Static);
if (property == null)
{
throw new InvalidOperationException(string.Format("Resource Type Does Not Have Property"));
}
if (property.PropertyType != typeof(string))
{
throw new InvalidOperationException(string.Format("Resource Property is Not String Type"));
}
return (string)property.GetValue(null, null);
}
return null;
}
}
当你编译时，属性值被硬编码到程序集中。如果你想在执行期间进行任何操作，你需要将常量作为键，然后将一些代码放入属性类本身以加载资源。
[System.AttributeUsage(System.AttributeTargets.Class, AllowMultiple = false)]
public class ProviderIconAttribute : Attribute
{
public Image ProviderIcon { get; protected set; }
public ProviderIconAttribute(Type resourceType, string resourceName)
{
var value = ResourceHelper.GetResourceLookup<Image>(resourceType, resourceName);
this.ProviderIcon = value;
}
}
//From https://dev59.com/6nM_5IYBdhLWcg3w9oSG
//Only thing I changed was adding NonPublic to binding flags since our images come from other dll's
// and making it generic, as the original only supports strings
public class ResourceHelper
{
public static T GetResourceLookup<T>(Type resourceType, string resourceName)
{
if ((resourceType != null) && (resourceName != null))
{
PropertyInfo property = resourceType.GetProperty(resourceName, BindingFlags.Public | BindingFlags.Static | BindingFlags.NonPublic);
if (property == null)
{
return default(T);
}
return (T)property.GetValue(null, null);
}
return default(T);
}
}
PublicResXFileCodeGenerator
然后将此添加到属性中：[Display(Name = "MyResourceName", ResourceType = typeof(Resources.MyResources))]
ErrorMessageResourceName和ErrorMessageResourceType参数。[Required(ErrorMessageResourceName ="attribute_name" , ErrorMessageResourceType = typeof(resource_file_type))]
我有一个类似的情况，需要将资源字符串放入属性中。在C# 6中，我们有nameof()功能，似乎可以解决这个问题。
在我的情况下，我可以使用[SomeAttribute(nameof(Resources.SomeResourceKey))]，它可以编译通过。然后，在另一端只需要做一些工作，使用该值从资源文件中获取正确的字符串。
在你的情况下，你可以尝试：
[IntegerValidation(1, 70, ErrorMessageResourceKey = nameof(Data.Messages.Speed))]
private int i_Speed;
Properties.Resources.ResourceManager.GetString(attribute.ErrorMessageResourceKey);
这是我写的一些东西，因为我找不到其他能做到这一点的东西。
输入
在项目A中编写一个常量字符串类。
[GenerateResource]
public static class ResourceFileName
{
public static class ThisSupports
{
public static class NestedClasses
{
[Comment("Comment value")]
public const string ResourceKey = "Resource Value";
}
}
}
输出
然后在项目中将生成一个包含常量类的资源。
你所需要做的就是在某个地方拥有这段代码：
源代码
public class CommentAttribute : Attribute
{
public CommentAttribute(string comment)
{
this.Comment = comment;
}
public string Comment { get; set; }
}
public class GenerateResourceAttribute : Attribute
{
public string FileName { get; set; }
}
public class ResourceGenerator
{
public ResourceGenerator(IEnumerable<Assembly> assemblies)
{
// Loop over the provided assemblies.
foreach (var assembly in assemblies)
{
// Loop over each type in the assembly.
foreach (var type in assembly.GetTypes())
{
// See if the type has the GenerateResource attribute.
var attribute = type.GetCustomAttribute<GenerateResourceAttribute>(false);
if (attribute != null)
{
// If so determine the output directory. First assume it's the current directory.
var outputDirectory = Directory.GetCurrentDirectory();
// Is this assembly part of the output directory?
var index = outputDirectory.LastIndexOf(typeof(ResourceGenerator).Assembly.GetName().Name);
if (index >= 0)
{
// If so remove it and anything after it.
outputDirectory = outputDirectory.Substring(0, index);
// Is the concatenation of the output directory and the target assembly name not a directory?
outputDirectory = Path.Combine(outputDirectory, type.Assembly.GetName().Name);
if (!Directory.Exists(outputDirectory))
{
// If that is the case make it the current directory.
outputDirectory = Directory.GetCurrentDirectory();
}
}
// Use the default file name (Type + "Resources") if one was not provided.
var fileName = attribute.FileName;
if (fileName == null)
{
fileName = type.Name + "Resources";
}
// Add .resx to the end of the file name.
fileName = Path.Combine(outputDirectory, fileName);
if (!fileName.EndsWith(".resx", StringComparison.InvariantCultureIgnoreCase))
{
fileName += ".resx";
}
using (var resx = new ResXResourceWriter(fileName))
{
var tuples = this.GetTuplesRecursive("", type).OrderBy(t => t.Item1);
foreach (var tuple in tuples)
{
var key = tuple.Item1 + tuple.Item2.Name;
var value = tuple.Item2.GetValue(null);
string comment = null;
var commentAttribute = tuple.Item2.GetCustomAttribute<CommentAttribute>();
if (commentAttribute != null)
{
comment = commentAttribute.Comment;
}
resx.AddResource(new ResXDataNode(key, value) { Comment = comment });
}
}
}
}
}
}
private IEnumerable<Tuple<string, FieldInfo>> GetTuplesRecursive(string prefix, Type type)
{
// Get the properties for the current type.
foreach (var field in type.GetFields(BindingFlags.Public | BindingFlags.Static))
{
yield return new Tuple<string, FieldInfo>(prefix, field);
}
// Get the properties for each child type.
foreach (var nestedType in type.GetNestedTypes())
{
foreach (var tuple in this.GetTuplesRecursive(prefix + nestedType.Name, nestedType))
{
yield return tuple;
}
}
}
}
然后创建一个小项目，其中包含对所有程序集的引用，并使用[GenerateResource]进行资源生成。
public class Program
{
static void Main(string[] args)
{
var assemblies = AppDomain.CurrentDomain.GetAssemblies().ToList();
string path = Directory.GetCurrentDirectory();
foreach (string dll in Directory.GetFiles(path, "*.dll"))
{
assemblies.Add(Assembly.LoadFile(dll));
}
assemblies = assemblies.Distinct().ToList();
new ResourceGenerator(assemblies);
}
}
ResourceFileName.ThisSupports.NestedClasses.ResourceKey，而其他代码可以使用资源文件。