How to Get the Start of the Week (Sunday or Monday) in C#?

Calculating the Week's Start Date in C#

This article demonstrates how to easily find the beginning of the week (either Sunday or Monday) in C#, using the current date and time. We'll accomplish this using a concise extension method.

Extension Method Implementation:

<code class="language-csharp">public static class DateTimeExtensions
{
    public static DateTime WeekStart(this DateTime dt, DayOfWeek firstDayOfWeek)
    {
        int dayDifference = (7 + (dt.DayOfWeek - firstDayOfWeek)) % 7;
        return dt.AddDays(-dayDifference).Date;
    }
}</code>

Usage Examples:

The WeekStart extension method simplifies the process of getting the week's start date. Here's how to use it:

• Monday as the first day:

<code class="language-csharp">DateTime mondayStart = DateTime.Now.WeekStart(DayOfWeek.Monday);</code>

• Sunday as the first day:

<code class="language-csharp">DateTime sundayStart = DateTime.Now.WeekStart(DayOfWeek.Sunday);</code>

This approach offers a clean and efficient way to determine the start of the week, regardless of whether you define it as Sunday or Monday.

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