How to write custom error message

[shujaatsiddiqui]

I want to concatenate property value into error message. I have a list of collection and I want to concatenate what item in the list satisfy the expression criteria.

{
        "RuleName": "CheckforVTPumpSelectionErrors121-03",
        "ErrorMessage": "WARNING: 121 - VT PUMP Manual Pick Required for {0} HP {1} pump!",
         "Expression": "ProductFamily.PumpConfigurations.Any(r => r.PumpDescription == \"Water Feature\" || r.PumpDescription == \"Transfer\") && Flag1 == false"
}

I want to replace {0} with horse power value.

My DTO:

public class ProductFamily
    {
        public int SCCR = 30;
        public List<PumpConfiguration> PumpConfigurations { get; set; }
    }

 public class PumpConfiguration
    {
        public PumpConfiguration()
        {
        }
        public string PumpDescription { get; internal set; }
        public int HP { get; internal set; }
    }

[abbasc52]

Hi @shujaatsiddiqui
We partially support writing custom error message. The syntax involves using $() around the variable. For e.g. $(input1)
you can find sample rule here:-

RulesEngine/test/RulesEngine.UnitTest/TestData/rules4.json

Line 8 in bafbff2

"ErrorMessage": "One or more adjust rules failed, with loyalityFactor : $(model1.loyalityFactor), country : $(model1.country), totalPurchasesToDate : $(model1.totalPurchasesToDate), model2 : $(model2)",

In your case you could use a local param to get the list item you want to print and then use it in error message.

Note: we only support basic parsing of error message, If you need more complex operations prefer using OutputExpression Action - https://microsoft.github.io/RulesEngine/#outputexpression

[shujaatsiddiqui]

It is not replacing it with properties values. I ran your test case from samples.

[ElanHasson]

I was able to accomplish similar with a custom action and a dynamic lambda parser on the context values

[shujaatsiddiqui]

can you please share some examples? or sample code?