How Can I Replace Only the First Occurrence of a String in .NET?

Replace first occurrence of a string in .NET

.NET provides several ways to replace the first occurrence of a specific string in a given text.

One way is to use a custom method, like the following example:

<code class="language-csharp">string ReplaceFirst(string text, string search, string replace)
{
  int pos = text.IndexOf(search);
  if (pos < 0) return text;
  return text.Substring(0, pos) + replace + text.Substring(pos + search.Length);
}</code>

This method searches for the first occurrence of "search" in "text" and replaces it with "replace". The logic is as follows:

• Use "IndexOf" to get the index.
• Check for not found by negative index.
• Concatenates the substring before occurrence with "replace" and the remaining substring after occurrence.

For example:

<code class="language-csharp">string str = "The brown brown fox jumps over the lazy dog";

str = ReplaceFirst(str, "brown", "quick");</code>

In addition, .NET provides the Regex.Replace(String, String, Int32) method, which has similar functionality. However, it may incur higher runtime costs due to its powerful parser.

In order to facilitate frequent use, you can create an extension method:

<code class="language-csharp">public static class StringExtension
{
  public static string ReplaceFirst(this string text, string search, string replace)
  {
     // ...与上面相同...
  }
}</code>

Using this extension method, the example can be simplified as follows:

<code class="language-csharp">str = str.ReplaceFirst("brown", "quick");</code>

The above is the detailed content of How Can I Replace Only the First Occurrence of a String in .NET?. For more information, please follow other related articles on the PHP Chinese website!