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Common Errors 03: Threw an exception of type 'System.Collections.Generic.KeyNotFoundException in C#

Common Errors 03: Threw an exception of type 'System.Collections.Generic.KeyNotFoundException in C# ?

Note - 'MyResult.ResultParameterSortedList[(int)PassOfNorms.PassingCriteriaIDs.My_Name]' threw an exception of type 'System.Collections.Generic.KeyNotFoundException'


The `KeyNotFoundException` error indicates that the key `(int)PassOfNorms.PassingCriteriaIDs.My_Name` does not exist in the `MyResult.ResultParameterSortedList` dictionary or sorted list. Here’s how you can troubleshoot and fix this issue:

1. Check if the Key Exists Before Accessing:

Before assigning the value, you can check if the key exists in the dictionary or sorted list using `ContainsKey` (for a dictionary) or `Contains` (for a sorted list).

For Dictionary:

if (MyResult.ResultParameterSortedList.ContainsKey((int)PassOfNorms.PassingCriteriaIDs.My_Name))
{
    MyResult.ResultParameterSortedList[(int)PassOfNorms.PassingCriteriaIDs.My_Name].Name = "Max Power (Kw)";
}
else
{
    // Handle the case where the key does not exist
    Console.WriteLine("Key not found: My_Name");
}

For SortedList:

if (MyResult.ResultParameterSortedList.Contains((int)PassOfNorms.PassingCriteriaIDs.My_Name))
{
    MyResult.ResultParameterSortedList[(int)PassOfNorms.PassingCriteriaIDs.My_Name].Name = "Max Power (Kw)";
}
else
{
    // Handle the case where the key does not exist
    Console.WriteLine("Key not found: My_Name");
}

2. Ensure the Key is Added:

If the key is expected to be in the list but isn't, you might need to add it first:

if (!MyResult.ResultParameterSortedList.ContainsKey((int)PassOfNorms.PassingCriteriaIDs.My_Name))
{
    // Create a new object with the appropriate type and add it to the list
    MyResult.ResultParameterSortedList[(int)PassOfNorms.PassingCriteriaIDs.My_Name] = new ResultParameter { Name = "Max Power (Kw)" };
}
else
{
    MyResult.ResultParameterSortedList[(int)PassOfNorms.PassingCriteriaIDs.My_Name].Name = "Max Power (Kw)";
}

3. Debugging:

- Check the Initialization: Ensure that `MyResult.ResultParameterSortedList` is properly initialized and populated with all expected keys before you attempt to access them.
- Inspect the Enumeration: Make sure that `PassOfNorms.PassingCriteriaIDs.My_Name` corresponds to a valid and correct value.

4. Exception Handling:

If you're unsure whether the key will be there and you want to handle it gracefully, you can wrap the code in a try-catch block:

try
{
    MyResult.ResultParameterSortedList[(int)PassOfNorms.PassingCriteriaIDs.My_Name].Name = "Max Power (Kw)";
}
catch (KeyNotFoundException)
{
    Console.WriteLine("Key not found: My_Name");
}

This approach ensures that your application doesn’t crash and gives you a chance to handle the missing key scenario appropriately.

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