Cast() vs. OfType() in LINQ: When to Use Which for Type Safety?

Differences between Cast() and OfType() in LINQ type conversion

When using LINQ to handle ArrayList and type conversion, the two methods Cast() and OfType() are particularly prominent. Understanding their differences is critical to effective type handling.

Comparison of Cast() and OfType()

Cast()：

• Attempts to convert all elements in the ArrayList to the specified type.
• If any element cannot be successfully converted, a InvalidCastException exception is raised.

OfType()：

• Only select elements that can be safely converted to the specified type.
• Ignore any elements that cannot be converted, effectively filtering them out.

How to use

• Cast(): Use this method when you are sure that all elements in the ArrayList can be converted to the required type. This approach is efficient but assumes the data is valid.
• OfType(): Use this method when you need to filter out elements that cannot be converted to the required type. It provides a safer way to prevent potential exceptions due to invalid conversions.

Example

Consider an array of objects:

<code class="language-csharp">object[] objs = new object[] { "12345", 12 };</code>

Use Cast() to convert this array:

<code class="language-csharp">objs.Cast<string>().ToArray();</code>

will cause a InvalidCastException exception because the element "12" cannot be converted to a string.

Use OfType() to convert:

<code class="language-csharp">objs.OfType<string>().ToArray();</code>

will produce an array with only one element:

<code class="language-csharp">{ "12345" }</code>

This demonstrates how OfType() can effectively filter out elements that cannot be safely converted.

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