Fix/duplicate msg

src/MiniValidation/TypeDetailsCache.cs

@@ -212,6 +212,15 @@ private static (ValidationAttribute[]?, DisplayAttribute?, SkipRecursionAttribut
             }
         }
 
+        // Deduplicate validation attributes by type and error message
+        if (validationAttributes is not null)
+        {
+            validationAttributes = validationAttributes
+                .GroupBy(a => a.GetType().FullName + ":" + a.FormatErrorMessage(property.Name))
+                .Select(g => g.First())
+                .ToList();
+        }
+
         return new(validationAttributes?.ToArray(), displayAttribute, skipRecursionAttribute);
     }
 

tests/MiniValidation.UnitTests/TryValidate.cs

@@ -464,4 +464,23 @@ public async Task TryValidateAsync_With_Attribute_Attached_Via_TypeDescriptor()
         Assert.Single(errors["PropertyToBeRequired"]);
         Assert.Single(errors["AnotherProperty"]);
     }
+
+
+    private class TestResults
+    {
+        [MinLength(3)]
+        public string ErrorCode { get; set; } = string.Empty;
+    }
+
+    [Fact]
+    public void MinLengthAttribute_ShouldNotProduceDuplicateErrors()
+    {
+        var testObj = new TestResults { ErrorCode = "12" };
+        var isValid = MiniValidator.TryValidate(testObj, out var errors);
+
+        Assert.False(isValid);
+        Assert.True(errors.ContainsKey(nameof(TestResults.ErrorCode)));
+        var errorMessages = errors[nameof(TestResults.ErrorCode)];
+        Assert.Single(errorMessages);
+    }  
 }