WebApi + ClientApp, GraphQL, Reflection

Events-WebApi/Events.WebAPI.Contract/Validation/ForeignKeyValueValidator.cs

@@ -0,0 +1,49 @@
+using FluentValidation;
+using MediatR;
+using Events.WebAPI.Contract.DTOs;
+using Events.WebAPI.Contract.Queries.Generic;
+
+namespace Events.WebAPI.Contract.Validation;
+
+public static class ForeignKeyValueValidatorExtension 
+{   
+  public static IRuleBuilderOptions<TCommand, TPK> ForeignKeyExists<TCommand, TDto, TPK>(
+    this IRuleBuilder<TCommand, TPK> ruleBuilder,
+    IMediator mediator,
+    IValidationMessageProvider validationMessageProvider,
+    ValidationMessage? validationMessage = null)
+    where TDto : IHasIdAsPK<TPK>
+    where TPK : IEquatable<TPK>
+  {
+    ValidationMessage message = validationMessage ?? validationMessageProvider.ForeignKeyNotFound("{PropertyName}");
+
+    return ruleBuilder.MustAsync(new ForeignKeyValueValidator<TCommand, TDto, TPK>(mediator).Validate)
+                      .WithMessage(message.Message)
+                      .WithErrorCode(message.Code);
+  }
+
+  private class ForeignKeyValueValidator<TCommand, TDto, TPK> where TDto : IHasIdAsPK<TPK> where TPK : IEquatable<TPK>
+  {      
+    private readonly IMediator mediator;
+
+    public ForeignKeyValueValidator(IMediator mediator)
+    {
+      this.mediator = mediator;
+    }
+
+    public async Task<bool> Validate(TCommand command, TPK value, ValidationContext<TCommand> validationContext, CancellationToken cancellationToken)
+    {
+      var query = new DoesItemExistsQuery<TDto, TPK>(value);
+      try
+      {
+        bool itemExists = await mediator.Send(query, cancellationToken);
+        return itemExists;
+      }
+      catch (Exception exc)
+      {
+        validationContext.AddFailure(exc.Message);
+        return false;
+      }
+    }
+  }
+}