.Net Interactive Polyglot notebook with "invalid" cell

Exceptions.ipynb

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    "# Exceptions\n",
    "\n",
    "**Syntax for throwing and catching**\n",
    "\n",
    "Just like other .NET languages, F# supports throwing and catching exceptions.  As with the [control flow expressions](./control-flow-expressions.ipynb), the syntax will feel familiar, but again there are a few catches that you should know about.\n",
    "\n",
    "## Defining your own exceptions\n",
    "\n",
    "When raising/throwing exceptions, you can use the standard system ones such as `InvalidOperationException`, or you can define your own exception types using the simple syntax shown below, where the \"content\" of the exception is any F# type:"
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    "exception MFSharpError1 of string\n",
    "exception MFSharpError2 of string * int"
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    "That's it! Defining new exception classes is a lot easier than in C#!\n",
    "\n",
    "## Throwing exceptions\n",
    "\n",
    "There are three basic ways to throw an exception\n",
    "\n",
    "* Using one of the built in functions, such as \"invalidArg\"\n",
    "* Using one of the standard .NET exception classes\n",
    "* Using your own custom exception types \n",
    "\n",
    "### Throwing exceptions, method 1: using one of the built in functions\n",
    "\n",
    "There are four useful exception keywords built into F#: \n",
    "\n",
    "* `failwith` throws a generic `System.Exception`\n",
    "* `invalidArg` throws an `ArgumentException`\n",
    "* `nullArg` throws a `NullArgumentException`\n",
    "* `invalidOp ` throws an `InvalidOperationException`\n",
    "\n",
    "These four probably cover most of the exceptions you would regularly throw. Here is how they are used:"
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    "// throws a generic System.Exception\n",
    "let f x =\n",
    "    if x then \"ok\"\n",
    "    else failwith \"message\""
   ]
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    "// throws an ArgumentException\n",
    "let f x =\n",
    "    if x then \"ok\"\n",
    "    else invalidArg \"paramName\" \"message\""
   ]
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    {
     "ename": "Error",
     "evalue": "(1,7): error CS1002: ; expected\r\n(1,10): error CS1525: Invalid expression term 'if'\r\n(1,10): error CS1002: ; expected\r\n(2,8): error CS1003: Syntax error, '(' expected\r\n(2,10): error CS1026: ) expected\r\n(2,15): error CS1002: ; expected\r\n(2,19): error CS1002: ; expected\r\n(2,19): error CS8641: 'else' cannot start a statement.\r\n(2,19): error CS1003: Syntax error, '(' expected\r\n(2,19): error CS1525: Invalid expression term 'else'\r\n(2,19): error CS1026: ) expected\r\n(2,19): error CS1525: Invalid expression term 'else'\r\n(2,19): error CS1002: ; expected\r\n(3,18): error CS1002: ; expected\r\n(3,30): error CS1002: ; expected",
     "output_type": "error",
     "traceback": [
      "(1,7): error CS1002: ; expected\r\n",
      "(1,10): error CS1525: Invalid expression term 'if'\r\n",
      "(1,10): error CS1002: ; expected\r\n",
      "(2,8): error CS1003: Syntax error, '(' expected\r\n",
      "(2,10): error CS1026: ) expected\r\n",
      "(2,15): error CS1002: ; expected\r\n",
      "(2,19): error CS1002: ; expected\r\n",
      "(2,19): error CS8641: 'else' cannot start a statement.\r\n",
      "(2,19): error CS1003: Syntax error, '(' expected\r\n",
      "(2,19): error CS1525: Invalid expression term 'else'\r\n",
      "(2,19): error CS1026: ) expected\r\n",
      "(2,19): error CS1525: Invalid expression term 'else'\r\n",
      "(2,19): error CS1002: ; expected\r\n",
      "(3,18): error CS1002: ; expected\r\n",
      "(3,30): error CS1002: ; expected"
     ]
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   "source": [
    "let f x =\n",
    "    if x then \"ok\"\n",
    "    else nullArg \"paramName\" \"message\""
   ]
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