Type casting object array members in C# causes an exception

Question

I have the following code which I am trying to debug

int ll(ref float[,] _lv) {
  object[] results = new object[20];

  results = func_v1(11, _lv);

}

Breaking to watch variable 'results' shows something like below

results {object[11]}
 + [0] {float[1,1]}
 + [1] {double[1,1]}
 + [2] {float[48,1]}
   ...
   ...
 + [10] {float[1,1]}

and I am not able to type cast to get values from it

float f = (float)results[0]; throws an invalid cast exception.

Please help me understand what exactly is this object array and how I can get values out of it.

regards. ak

why the downvote? question looks reasonable to me. upvoted.

x0n
– x0n

2012-10-03 17:51:13 +00:00
Commented Oct 3, 2012 at 17:51 — x0n
– x0n, Commented Oct 3, 2012 at 17:51

Dharun · Accepted Answer · 2012-10-03 17:50:20Z

5

You're using a multidimensional array which you can read about here: http://msdn.microsoft.com/en-us/library/2yd9wwz4(v=vs.71).aspx

You need to cast it appropriately

var f = (float[,])results[0]

answered Oct 3, 2012 at 17:50

Dharun

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2 Comments

Kamil Over a year ago

...but remember, that var f now will be an array of floats.

Dharun Over a year ago

A two-dimensional array of floats.

Henk Holterman · Accepted Answer · 2012-10-03 17:50:08Z

1

float f = (float)results[0]; throws an invalid cast exception.

I think you need

float[,] f = (float[,])results[0];
double[,] d = (double[,])results[1];

answered Oct 3, 2012 at 17:50

Henk Holterman

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Comments

x0n · Accepted Answer · 2012-10-03 17:50:20Z

1

The item at index 0 is not a float - it's a float[,].

answered Oct 3, 2012 at 17:50

x0n

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Comments

Rob · Accepted Answer · 2012-10-03 17:56:32Z

0

Clearly object[] results doesn't have floats in it. You need to go into func_v1 and see what it is returning. Evidently its returning something that is getting downcasted to object's, which could be anything. From the output you pasted it looks like it is returning an object array with a mix of two-dimensional floats and doubles.

You could attempt to cast (float[,])results[0], but obviously that will blow up when you do it on an item that is in reality a double[,]. If you can't change func_v1() you will need to have an switch on the type of the item.

i.e.: if (results[0].GetType() == typeof(float[,]))

answered Oct 3, 2012 at 17:56

Rob

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