How to deal specifically with a Keynotfoundexception?

Question

I have a doubt, I tried to find some content on Google but I did not find.

I have a block try catch as follows:

try
{
    //código
    string idFormaPgto = Dictionaries.FormaPgto[_order.FK_PEDIDOS_FORMA_PAGAMENTO];
    //restante do código
}
catch(Exception e)
{

}

The problem is sometimes I’ll get one KeyNotFoundException but the following code MUST continue and I need to set a standard vallor to idFormaPgto, I don’t know if there’s a more elegant and correct way to treat this, what I thought was:

try
{
    //código
    string idFormaPgto = "";
    try
    {
       idFormaPgto = Dictionaries.FormaPgto[_order.FK_PEDIDOS_FORMA_PAGAMENTO];
    }
    catch(Exception e)
    {
       idFormaPgto = "1"; //tratamento do idFormaPgto 
    }
    //restante do código
}
catch(Exception e)
{

}

My code solves the problem, but I believe it is not the most correct way to do this, perhaps using some class extension method Dictionary but I don’t know any. The goal is to treat this KeyNotFoundException unused try catch inside try catch

Answer 1

You can simply use the method TryGetValue. This method attempts to get the value by the given key and, if the key does not exist, returns the type pattern.

string idFormaPgto;
Dictionaries.FormaPgto.TryGetValue[_order.FK_PEDIDOS_FORMA_PAGAMENTO, out idFormaPgto];

If you want to shorten a little more idea and make it more like the method FirstOrDefault from LINQ, it is possible to write an extension method for dictionaries.

For example:

using System;
using System.Collections.Generic;

public class Program
{
    public static void Main()
    {
        var dicio = new Dictionary<int, string>
        {
            { 65, "A" },
            { 74, "J" },
            { 69, "E" }
        };

        Console.WriteLine(dicio.GetByKeyOrDefault(65) ?? "Chave inexistente");
        Console.WriteLine(dicio.GetByKeyOrDefault(80) ?? "Chave inexistente");
        Console.WriteLine(dicio.GetByKeyOrDefault(69) ?? "Chave inexistente");
    }
}

public static class DictionaryExtensions
{
    public static TValue GetByKeyOrDefault<TKey, TValue>(this IDictionary<TKey, TValue> dict, TKey key)
        => dict.ContainsKey(key) ? dict[key] : default(TValue); 
}

^{See working on . NET Fiddle}

Note that in the implementation of the method, GetByKeyOrDefault it is still possible to do one more micro-optimization and use the method TryGetValue not to need to make two queries in the dictionary (one in the method ContainsKey and another when obtaining the value).

Answer 2

You can simply use the Linq, as in the example below:

var dicionario= new Dictionary<string, string> {
    { "teste 1", "1" },
    { "testando", "2" },
};

var idFormaPgto = dicionario.SingleOrDefault(x=> x.Key.Equals(_order.FK_PEDIDOS_FORMA_PAGAMENTO)).Value ?? "1";

Edit As argued in the comments this is a basic approach and should only be considered in a point application. It is important to pay attention to the observations made by

Linq: That way you lose all idea of using a dictionary. The method Singleordefault will get an enumerator, move it item by item and do the validation of each of them. You simply throw out the main reason for a dictionary which is to have search complexity O(1) and passes to have search complexity O(N)

Answer 3

You can use the method Containskey, in which you pass the key who is searching and will be returned whether or not she exists in your collection Dictionary.

string idFormaPgto = "1";

//Se a key existir no seu Dictionary nós iremos pegar o valor, senão iremos manter o valor 1
if (Dictionaries.ContainsKey[_order.FK_PEDIDOS_FORMA_PAGAMENTO])
      idFormaPgto = Dictionaries[_order.FK_PEDIDOS_FORMA_PAGAMENTO];

If you want to do with a ternary condition it would be as follows:

    string idFormaPgto = Dictionaries.ContainsKey[_order.FK_PEDIDOS_FORMA_PAGAMENTO] ? Dictionaries[_order.FK_PEDIDOS_FORMA_PAGAMENTO] : "1";