There are various methods to remove unicode characters from a String in .NET.
Below i will show you some methods and the benchmark results.
Before choosing a method, take a look at the Benchmark result and the Framework Compatibility.

Benchmark Summary

A for Loop removed 100 000 times the unicode characters of the string value
ᾭHeὣlݬl♫oѪ₪ Wor♀ld. This has been repeated 40 Times for each method. All Methods returned the right result Hello World.

Methods

Remove Unicode Characters using Regex

C# Version

public static String StripUnicodeCharactersFromString(string inputValue)
{
       return Regex.Replace(inputValue, @"[^\u0000-\u007F]", String.Empty);
}

VB.NET Version

Private Function ConvertToASCIIUsingRegex(inputValue As String) As String
	Return Regex.Replace(inputValue, "[^\u0000-\u007F]", String.Empty)
End Function

Compatibility: .NET 2.0 .NET 3.0 .NET 3.5 .NET 4.0 .NET 4.5

Remove Unicode Characters using Regex (Compiled)

C# Version

private static Regex _compiledUnicodeRegex = new Regex(@"[^\u0000-\u007F]", RegexOptions.Compiled);

public static String StripUnicodeCharactersFromString(string inputValue)
{
	return _compiledUnicodeRegex.Replace(inputValue, String.Empty);
}

VB.NET Version

Private _compiledUnicodeRegex As New Regex("[^\u0000-\u007F]", RegexOptions.Compiled)
Public Function StripUnicodeCharactersFromString(inputValue As String) As [String]
	Return _compiledUnicodeRegex.Replace(inputValue, [String].Empty)
End Function

Compatibility: .NET 2.0 .NET 3.0 .NET 3.5 .NET 4.0 .NET 4.5

Remove Unicode Characters using String Normalization

C# Version

public static String StripUnicodeCharactersFromString(string inputValue)
{
	StringBuilder newStringBuilder = new StringBuilder();
	newStringBuilder.Append(inputValue.Normalize(NormalizationForm.FormKD).Where(x => x < 128).ToArray());
	return newStringBuilder.ToString();
}

VB.NET Version

Public Function StripUnicodeCharactersFromString(inputValue As String) As [String]
	Dim newStringBuilder As New StringBuilder()
	newStringBuilder.Append(inputValue.Normalize(NormalizationForm.FormKD).Where(Function(x) Convert.ToInt32(x) < 128).ToArray())
	Return newStringBuilder.ToString()
End Function

Compatibility: .NET 2.0 .NET 3.0 .NET 3.5 .NET 4.0 .NET 4.5

Remove Unicode Characters using Encodings

C# Version

public static String StripUnicodeCharactersFromString(string inputValue)
{
	return Encoding.ASCII.GetString(Encoding.Convert(Encoding.UTF8, Encoding.GetEncoding(Encoding.ASCII.EncodingName, new EncoderReplacementFallback(String.Empty), new DecoderExceptionFallback()), Encoding.UTF8.GetBytes(inputValue)));
}

VB.NET Version

Public Function StripUnicodeCharactersFromString(inputValue As String) As [String]
	Return Encoding.ASCII.GetString(Encoding.Convert(Encoding.UTF8, Encoding.GetEncoding(Encoding.ASCII.EncodingName, New EncoderReplacementFallback([String].Empty), New DecoderExceptionFallback()), Encoding.UTF8.GetBytes(inputValue)))
End Function

Compatibility: .NET 2.0 .NET 3.0 .NET 3.5 .NET 4.0 .NET 4.5

Remove Unicode Characters using LINQ

C# Version

public static String StripUnicodeCharactersFromString(string inputValue)
{
	return new string(inputValue.Where(c => c <= sbyte.MaxValue).ToArray());
}

VB.NET Version

Public Function StripUnicodeCharactersFromString(inputValue As String) As [String]
	Return New String(inputValue.Where(Function(c) Convert.ToInt32(c) <= SByte.MaxValue).ToArray())
End Function

Compatibility: .NET 2.0 .NET 3.0 .NET 3.5 .NET 4.0 .NET 4.5

Do you have an alternate or faster method for removing unicode?

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Related links:

• ASCII Table and Description
• Unicode
• Difference between ascii and unicode
• How does RegexOptions.Compiled work?
• To Compile or Not To Compile