ArgumentOutOfRangeException Was Unhandled

问题

Further details of the exception: Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index

When reading the exception, I understand what it's trying to tell me. What I don't understand is -why- it's coming up. Here is the snippet of relevant code:

        //the model contains more than one mesh, so each
        //one must be accounted for in the final sphere
        List<BoundingSphere> spheres = new List<BoundingSphere>();
        int index = 0;

        //cycle through the meshes
        foreach (ModelMesh mesh in this.model.Meshes)
        {
            //and grab its bounding sphere
            spheres[index++] = mesh.BoundingSphere; //<- this is the line that throws the exception
        } //end foreach

While debugging, I can see in the table provided by Visual Studio that my model.Meshes.Count is 5, and that at the current iteration, index is 1. Index is less than the size of my collection, and it is non-negative.

What's throwing the exception? I've tried searching for similar examples, but haven't found anything to quite answer my question yet.

Thanks in advance.

回答1:

You need to use list.Add(...) instead of indexing.

List's size is 0 by deafult and you can add items, but you code indexing non-existent item. It will fail even on index = 0.

回答2:

You meant to write spheres.Add(mesh.BoundingSphere). Your spheres list is empty after you created it. You cannot access an item which is not there.

回答3:

You need to use the Add method to increase the size of the list. So try spheres.Add(mesh.BoundingSphere); rather than spheres[index++] = mesh.BoundingSphere;

来源：https://stackoverflow.com/questions/7480087/argumentoutofrangeexception-was-unhandled

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