[英]Using DB Context in a Custom Validation Attribute
我正在嘗試在Core 2項目中創建一個驗證屬性。 它需要對照數據庫中保存的現有值列表來驗證該值。
下面的代碼不起作用,它無法訪問數據庫上下文。
任何想法為什么/如何糾正?
public class BibValidatorAttribute : ValidationAttribute
{
protected override ValidationResult IsValid(
object value, ValidationContext validationContext)
{
RaceEntryViewModel raceEntry = (RaceEntryViewModel)validationContext.ObjectInstance;
ApplicationDbContext _context = new ApplicationDbContext();
var dbraceEntry = _context.RaceEntries.FirstOrDefault(c => c.Id == raceEntry.Id);
if(raceEntry.BibNumber != dbraceEntry.BibNumber)
{
if (value != null)
{
var raceentries = from r in _context.RaceEntries
select r;
var mycount = raceentries.Count(c => c.BibNumber == raceEntry.BibNumber);
if (mycount != 0)
{
return new ValidationResult("The bib number entered already exists");
}
else
{
return ValidationResult.Success;
}
}
else
{
return ValidationResult.Success;
}
}
else
{
return ValidationResult.Success;
}
}
}
我發現您可以做的是從ValidationContext中檢索數據庫上下文,但我沒有意識到您可以使用GetService完成。
var _context = (ApplicationDbContext)validationContext
.GetService(typeof(ApplicationDbContext));
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