Class

# KeyNotFoundException

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## Description

You tried to access an item in a `Dictionary</api/language/dictionary>` using a key that is not in the `Dictionary</api/language/dictionary>`.

## Properties

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| Name                                            | Type                               | Read-Only | Shared |
|-------------------------------------------------|------------------------------------|-----------|--------|
| `ErrorNumber<keynotfoundexception.errornumber>` | `Integer</api/data_types/integer>` |           |        |
| `Message<keynotfoundexception.message>`         | `String</api/data_types/string>`   |           |        |

## Methods

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| Name                                             | Parameters                                                                                              | Returns                                    | Shared |
|--------------------------------------------------|---------------------------------------------------------------------------------------------------------|--------------------------------------------|--------|
| `Constructor<keynotfoundexception.constructor0>` | message As `String</api/data_types/string>` = "", errorNumber As `Integer</api/data_types/integer>` = 0 |                                            |        |
| `Stack<keynotfoundexception.stack>`              |                                                                                                         | `String()</api/data_types/string>`         |        |
| `StackFrames<keynotfoundexception.stackframes>`  |                                                                                                         | `StackFrame()</api/exceptions/stackframe>` |        |

## Property descriptions

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KeyNotFoundException.ErrorNumber

**ErrorNumber** As `Integer</api/data_types/integer>`

> Used to contain an error number that describes the runtime error.

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KeyNotFoundException.Message

**Message** As `String</api/data_types/string>`

> Used to contain descriptive text to display when the runtime exception is encountered.

## Method descriptions

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KeyNotFoundException.Constructor

**Constructor**(message As `String</api/data_types/string>` = "", errorNumber As `Integer</api/data_types/integer>` = 0)

> <div class="note">
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> <div class="title">
>
> Note
>
> </div>
>
> `Constructors</api/language/constructor>` are special methods called when you create an object with the `New</api/language/new>` keyword and pass in the parameters above.
>
> </div>
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> Used to raise your own `RuntimeException</api/exceptions/runtimeexception>` with a *message* and optional error number.

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KeyNotFoundException.Stack

**Stack** As `String()</api/data_types/string>`

> Returns a `String</api/data_types/string>` array that contains a list of all of the methods in the stack from the main entrypoint to the point at which the exception was invoked.
>
> The stack contains all the method names up and including the current method name.
>
> This feature only works if the **IncludeFunctionNames** property on the App object is selected in the Shared Build Settings.
>
> In addition to your own method calls, you will also see framework method calls, but these may not always be completely accurate due to insufficient symbols for the OS to resolve.

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KeyNotFoundException.StackFrames

**StackFrames** As `StackFrame()</api/exceptions/stackframe>`

> Returns an array containing the stack when the exception was first raised.

## Notes

You can avoid this exception by making use of the `Dictionary.Lookup<dictionary.lookup>` method to provide a default value if the key is not found or by using the `Dictionary.HasKey<dictionary.haskey>` method to check if the key exists.

## Sample code

The following `For...Next</api/language/loops/for...next>` loop produces a <span class="title-ref">KeyNotFoundException</span> error when the loop runs with the counter equal to 1. The value of 1 — which is a `Variant</api/data_types/variant>`, not an `Integer</api/data_types/integer>` — has just been removed.

``` xojo
Var d As New Dictionary
Var i As Integer
d.Value(0) = "Clark Kent"
d.Value(1) = "Lois Lane"
d.Value(2) = "Jimmy Olsen"
d.Remove(1)
For i = 0 To d.Count - 1  ' fails when i=1
  ListBox1.Addrow(d.Value(i))
Next
```

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To handle the error, add an `Exception</api/exceptions/exception>` block to the end of the method, such as:

``` xojo
Exception err As KeyNotFoundException
  MessageBox("You tried to access a nonexistent item!")
```

## Compatibility

|                       |     |
|-----------------------|-----|
| **Project Types**     | All |
| **Operating Systems** | All |

<div class="seealso">

`RuntimeException</api/exceptions/runtimeexception>` parent class; `Dictionary</api/language/dictionary>` class; `Exception</api/exceptions/exception>` block.

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