Where clause filtering in C Sharp (C#) - Step-by-Step Execution

Concept Flow - Where clause filtering

Start with full dataset

↓

Apply WHERE condition

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Check each row

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Include row

↓

Filtered result set

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End

Filtering data by checking each row against a condition and keeping only those that match.

Execution Sample

C Sharp (C#)

var filtered = people.Where(p => p.Age > 30);

Filters the list 'people' to include only those with Age greater than 30.

Execution Table

Step	Person Name	Person Age	Condition (Age > 30)	Include in Result
1	Alice	25	25 > 30 = False	No
2	Bob	35	35 > 30 = True	Yes
3	Charlie	30	30 > 30 = False	No
4	Diana	40	40 > 30 = True	Yes
5	Eve	28	28 > 30 = False	No

💡 All rows checked; only those with Age > 30 included.

Variable Tracker

Variable	Start	After 1	After 2	After 3	After 4	After 5	Final
filtered count	0	0	1	1	2	2	2

Key Moments - 2 Insights

Why is Charlie not included even though his age is 30?

Because the condition is strictly greater than 30 (Age > 30). 30 is not greater than 30, so Charlie is excluded as shown in step 3 of the execution_table.

Does the WHERE clause change the original data?

No, it only filters and returns a new collection. The original 'people' list remains unchanged, as the WHERE clause just selects matching rows.

Visual Quiz - 3 Questions

Look at the execution_table, how many people are included in the filtered result?

A 4

B 3

C 2

D 1

💡 Hint

Check the 'Include in Result' column in the execution_table for rows marked 'Yes'.

At which step does the condition first evaluate to True?

A Step 2

B Step 1

C Step 3

D Step 4

💡 Hint

Look at the 'Condition (Age > 30)' column in the execution_table to find the first 'True'.

If the condition changed to Age >= 30, which person would be included additionally?

A Alice

B Charlie

C Eve

D No one else

💡 Hint

Check step 3 in execution_table where Age is exactly 30 and see if condition would be true with >=.

Concept Snapshot

WHERE clause filters rows based on a condition.
Syntax: collection.Where(row => condition).
Only rows meeting condition are included.
Original data stays unchanged.
Useful for selecting specific data from tables or lists.

Full Transcript

The WHERE clause filtering process starts with a full dataset. Each row is checked against a condition. If the condition is true, the row is included in the result; otherwise, it is excluded. For example, filtering people with Age > 30 checks each person's age. Only those older than 30 are kept. This does not change the original data but returns a new filtered collection. The execution table shows step-by-step how each person is tested and whether they are included. Key points include understanding strict vs inclusive conditions and that filtering does not modify original data.