Initializing an array based on the present values

Question

I want to initialize an c# array. I don't know in advance how many values I am going to store on it. I know that this number will be between 0 and 5.

Is this the best approach to do this?

private CompiledRuleMethod CompileRuleMethod(Rule r)
{
  int sizeParameters = 0;
  if (r.Param1 != "") sizeParameters++;
  if (r.Param2 != "") sizeParameters++;
  if (r.Param3 != "") sizeParameters++;
  if (r.Param4 != "") sizeParameters++;
  if (r.Param5 != "") sizeParameters++;
  object[] parameters = new object[sizeParameters];
  if (r.Param1 != "") parameters[0] = r.Param1;
  if (r.Param2 != "") parameters[1] = r.Param2;
  if (r.Param3 != "") parameters[2] = r.Param3;
  if (r.Param4 != "") parameters[3] = r.Param4;
  if (r.Param5 != "") parameters[4] = r.Param5;

  return new CompiledRuleMethod(DelegateFactory.Create(typeof(RuleMethod).GetMethod(r.MethodName)),parameters);
}

I am pretty sure that isn't.

Why parameters is a object[] whereas the ParamXs are all strings? — Sweeper
– Sweeper, Commented Jul 4, 2019 at 6:17
Is the ParamX, properties from r, really look alike? Could we use reflexion to find all properties of r then filter, and map the value to an array? With some like foreach(property p in object) — xdtTransform
– xdtTransform, Commented Jul 4, 2019 at 6:19
what is r? why dont you make a method like "r.size()" that check all those params internally? — ΦXocę 웃 Пepeúpa ツ
– ΦXocę 웃 Пepeúpa ツ, Commented Jul 4, 2019 at 6:20
Do you really need an array ? If you don't know in advance how many elements will be stored, use a List instead. — Martin Verjans
– Martin Verjans, Commented Jul 4, 2019 at 6:20

Sweeper · Accepted Answer · 2019-07-04 06:25:25Z

1

Note that your current code doesn't actually work. If, say, only Param4 is empty, then sizeParameters is 4. And then you create a parameters array of length 4. However, when the execution reaches the last line, it will try to put Param5 into index 4 of the array, causing an IndexOutofRangeException.

It seems like you just want to filter out those params that are empty, and keep the ones that are not empty.

You can first put all of the params you want into an array:

var unfilteredParams = new[] {r.Param1, r.Param2, r.Param3, r.Param4, r.Param5};

And then use Where to filter it:

var filteredParams = unfilteredParams.Where(x => x != "").ToArray();

answered Jul 4, 2019 at 6:25

Sweeper

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4 Comments

Dmitrii Bychenko Over a year ago

.Cast<object>() since we want object[] parameters

Sweeper Over a year ago

@DmitryBychenko Declaring the type of filteredParams as object[] works as well, since ToArray is generic, but I don't see why the OP would want an object array instead.

Javier Over a year ago

@Sweeper, you are right. But i am going to ensure that always the parameters are going to be filled in order. I mean, if for example Param3 is empty, Param4 and Param5 will be empty.

Javier Over a year ago

Yes, I tested and it works perfectly. Now I have to work on type conversion.

see sharper · Accepted Answer · 2019-07-04 06:23:43Z

0

Don't use an array. List is more appropriate if you don't know how many items it will need. Then you can use list.Add(r.Param) to append items. Though without more context it's hard to say what is the best approach.

answered Jul 4, 2019 at 6:23

see sharper

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