[英]Writing a generic Resolver in AutoMapper?
我想編寫一個通用AutoMapper的解析器來更改Model的文件路徑。
沒有通用解析器,我編寫了以下解析器:
例如:
public class UserPhotoPathResolver : ValueResolver<User, string>
{
protected override string ResolveCore(User source)
{
var url = new UrlHelper(HttpContext.Current.Request.RequestContext);
return url.Content(string.IsNullOrWhiteSpace(source.PhotoPath)
? StaticVariables.DefaultUserImagePath
: source.PhotoPath);
}
}
現在,我編寫了以下解析器:
public class FilePathResolver<T, TProperty> : ValueResolver<T, string> where T : class
{
private readonly Expression<Func<T, TProperty>> _propertyExpression;
public FilePathResolver(Expression<Func<T, TProperty>> propertyExpression)
{
_propertyExpression = propertyExpression;
}
protected override string ResolveCore(T source)
{
Type typeOfEntity = typeof(T);
MemberExpression member = _propertyExpression.Body as MemberExpression;
if (member == null)
throw new ArgumentException(string.Format("Expression '{0}' refers to a method, not a property.", _propertyExpression));
PropertyInfo propInfo = member.Member as PropertyInfo;
if (propInfo == null)
throw new ArgumentException(string.Format("Expression '{0}' refers to a field, not a property.", _propertyExpression));
if (typeOfEntity != propInfo.ReflectedType && !typeOfEntity.IsSubclassOf(propInfo.ReflectedType))
throw new ArgumentException(string.Format("Expresion '{0}' refers to a property that is not from type {1}.", _propertyExpression, typeOfEntity));
string filePath = Convert.ToString(ModelHelpers.GetStringPropertyValue(source, propInfo.Name));
return string.IsNullOrWhiteSpace(filePath)
? string.Empty
: UrlHelpers.GetUrlHelperInstance().Content(filePath);
}
}
public static object GetStringPropertyValue(object src, string propertyName)
{
return src.GetType().GetProperty(propertyName).GetValue(src, null);
}
public static TProperty GetValue<T, TProperty>(T obj, Expression<Func<T, TProperty>> expression) where T : class
{
if (obj == null) return default(TProperty);
Func<T, TProperty> func = expression.Compile();
return func(obj);
}
但是FilePathResolver
返回此字符串MyApp.Classes.Helpers.FilePathResolver%602[MyApp.DAL.ModelName,System.String]
我正在使用以下解析器:
Mapper.CreateMap<EntityClass, EntityClassModel>()
.ForMember(m => m.ResolvedLogoPath, opt => opt.ResolveUsing(m => new FilePathResolver<EntityClass, string>(p => p.LogoPath)));
我該怎么做?
問題是使用了錯誤的ResolveUsing方法重載。
但是您需要以下一個。
您可以通過以下方式更改映射配置來修復它。
Mapper.CreateMap<EntityClass, EntityClassModel>()
.ForMember(m => m.ResolvedLogoPath,
opt => opt.ResolveUsing<FilePathResolver<EntityClass, string>>()
.ConstructedBy(() => new FilePathResolver<EntityClass, string>(p => p.LogoPath)));
甚至像這樣:
Mapper.CreateMap<EntityClass, EntityClassModel>()
.ForMember(m => m.ResolvedLogoPath,
opt => opt.ResolveUsing(new FilePathResolver<EntityClass, string>(p => p.LogoPath)));
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