Cannot index into null array powershell

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It works if I run it from the powershell command line it updates the SP list , but it does display an error message "Cannot index into a null array. I am kind of new to powershell but in vb I could use "On Error Resume Next" which is not great but would work. How can I tell powershell to not assign null values to empty array elements? Cannot index into a null array. We can actually chain them in the pipeline but that is an advanced technique. Figure this out first.

The pipeline knows how to filter out nulls. Here is a cleaner approach. Try not to over comment. Let code do the commenting for you by choosing useful variable names. I cannot test this because I do not have your server.

It will be easier for you to see what is happening. YOu use of arrays was not really workable. No - you code will not work as expected due to multiple logic errors. Start with the structure I posted as it correctly models the solution. It is also much simpler. You are having an issue of how to turn rows into columns. We can use the same index to update existing items in the array.

This gives us direct access to update individual items. If we try to update an item that is past the last element, then we get an Index was outside the bounds of the array. At some point, you might need to walk or iterate the entire list and perform some action for each item in the array. Arrays and the PowerShell pipeline are meant for each other.

This is one of the simplest ways to process over those values. When you pass an array to a pipeline, each item inside the array is processed individually.

You can use either one because they both represent the current object in the pipeline. The ForEach loop works well with collections. I tend to forget about this one but it works well for simple operations.

PowerShell allows you to call. ForEach on a collection. You can drop the parentheses and just provide the script block. This is a lesser known syntax but it works just the same. This foreach method was added in PowerShell 4. The for loop is used heavily in most other languages but you don't see it much in PowerShell. When you do see it, it's often in the context of walking an array.

Finally, we specify that every time we loop that me must increase the index by 1. Whenever you're using a for loop, pay special attention to the condition. It's easy to get the condition slightly wrong to get an off-by-one error in your logic.

That would cause your result to process too many or too few items. This is the classic off-by-one error. This is one that is easy to overlook. If you provide an array to a switch statement , it checks each item in the array. There are a lot of cool things that we can do with the switch statement. I have another article dedicated to this. When your array is a collection of string or integers value types , sometimes you may want to update the values in the array as you loop over them.

Most of the loops above use a variable in the loop that holds a copy of the value. If you update that variable, the original value in the array is not updated. The exception to that statement is the for loop. If you want to walk an array and update values inside it, then the for loop is what you're looking for. This example takes a value by index, makes a few changes, and then uses that same index to assign it back. So far, the only thing we've placed in an array is a value type, but arrays can also contain objects.

All of the basic features we already talked about still apply to arrays of objects with a few details worth pointing out. But PowerShell offers us the ability to request LastName directly.

PowerShell enumerates them all for us and returns a clean list. This is where Where-Object comes in so we can filter and select what we want out of the array based on the properties of the object.

Arrays have a Where method on them that allows you to specify a scriptblock for the filter. With value types, the only way to update the array is to use a for loop because we need to know the index to replace the value. We have more options with objects because they are reference types. Here is a quick example:. So updates to its properties do update the original. You still can't replace the whole object this way.

This doesn't work like you would expect:. The -join operator is the most obvious one so let's look at it first. I like the -join operator and use it often. It joins all elements in the array with the character or string that you specify. One of the features that I like about the -join operator is that it handles single items.

Here is a clever trick that Lee Dailey pointed out to me. If you ever want to join everything without a delimiter, instead of doing this:. You can use -join with the array as the parameter with no prefix. Take a look at this example to see that I'm talking about. The other operators like -replace and -split execute on each item in the array.

I can't say that I have ever used them this way but here is an example.