LINQ Casting: When to Use Cast() vs. OfType()?

Type conversion methods in LINQ: Comparison of Cast() and OfType()

When using LINQ for type conversion, there are two main methods used: Cast() and OfType(). Understanding the nuances of these two approaches is critical for efficient data manipulation.

Cast() method

The

Cast() method attempts to convert each element in IEnumerable to the specified target type. It does not perform any filtering operations; it simply attempts to convert all elements. If some elements cannot be successfully converted, this may result in a InvalidCastException exception.

OfType() method

The

OfType() method filters elements based on their type before converting them. It returns a IEnumerable containing only those elements that can be safely converted to the target type.

Usage scenarios

When to use each method depends on the desired behavior:

• When to use Cast():

  • You want to intentionally convert all elements, even if it might cause an exception.
  • You are sure that every element can be converted safely.

• When to use OfType():

  • You only want to retrieve elements that are safe to convert.
  • You want to filter out elements that cannot be converted.

Example description

Consider the following example:

object[] objs = new object[] { "12345", 12 };
IEnumerable<string> castCollection = objs.Cast<string>().ToArray(); // 抛出 InvalidCastException 异常
IEnumerable<string> ofTypeCollection = objs.OfType<string>().ToArray(); // 返回 { "12345" }

In this example, Cast() will try to convert all elements, causing a InvalidCastException exception. However, OfType() filters out the integer elements and only returns "12345".

Summary

By understanding the difference between Cast() and OfType(), developers can perform more targeted and efficient type conversion operations in LINQ queries, resulting in clearer, more robust code.

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