WebApi + ClientApp, GraphQL, Reflection

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

@@ -0,0 +1,36 @@
+using Events.WebAPI.Contract.Queries.Generic;
+using FluentValidation;
+using MediatR;
+
+namespace Events.WebAPI.Contract.Validation;
+
+public static class NoChildRecordsValidatorExtension
+{   
+  public static IRuleBuilderOptions<TCommand, TPK> NoChildRecords<TCommand, TDto, TPK>(this IRuleBuilder<TCommand, TPK> ruleBuilder, string columnName, IMediator mediator)     
+  {
+    return ruleBuilder.MustAsync(new NoChildRecordsValidator<TDto, TPK>(columnName, mediator).Validate)
+                      .WithMessage("Cannot delete entity {PropertyValue} because there are child records in table related to " + typeof(TDto).Name.ToString());
+  }
+
+  private class NoChildRecordsValidator<TDto, TPK>
+  {
+    private readonly string columnName;
+    private readonly IMediator mediator;
+
+    public NoChildRecordsValidator(string columnName, IMediator mediator)
+    {
+      this.columnName = columnName;
+      this.mediator = mediator;
+    }
+
+    public async Task<bool> Validate(TPK value, CancellationToken cancellationToken)
+    {        
+      var query = new GetCountQuery<TDto>()
+      {
+        Filters = $"{columnName}=={value}"             
+      };
+      int count = await mediator.Send(query, cancellationToken);
+      return count == 0;
+    }
+  }
+}