Just for the sake of completeness I want to provide some implementation. /// Check if string is Base64 Span buffer = new Span(new byte[bas byte[] newBytes = Convert.FromBase64String(s); Console.WriteLine("The restored byte array: "); Console.WriteLine(" {0}\n", BitConverter.ToString(newBytes)); } } // The example displays the //MemoryStream stream = new MemoryStream(Convert.FromBase64String(image)); Want to build the ChatGPT based Apps? All that you can determine is that the string contains only characters that are valid for a base64 encoded string. It may not be possible to determine that the string is the base64 encoded version of some data. for example test1234 is a valid base64 encoded string, and when you decode it you will get some bytes. The Base64 validator checks whether the submitted text is a valid Base64 encoded string. It allows you to validate online a variety of Base64 standards. Therefore, try to specify another standard, if one of them failed. If you do not know which standard to choose, check the standard detector. If you want to decode a string, use the Base64 decoder. public static bool IsBase64String(string base64) {. Do decode, re encode and compare the result to original string public static Boolean IsBase64(this String str) I know you said you didn't want to catch an exception. But, because catching an exception is more reliable, I will go ahead and post this answer. It allows you to validate online a variety of Base64 standards. 0. xxxxxxxxxx. Why not just catch the exception, and return False? This avoids additional overhead in the common case. i want to validate input string is Valid Base64String or not, if its valid then convert into byte[]. Parameters specify the Just for the sake of completeness I want to provide some implementation. I believe the regex should be: Regex.IsMatch(s, @"^[a-zA-Z0-9\+/]*={0,2}$") Span buffer = new Span(new The answer must depend on the usage of the string. There are many strings that may be "valid base64" according to the syntax suggested by several p Why not just catch the exception, and return False? This avoids additional overhead in the common case. ToBase64String(Byte[], Int32, Int32) Converts a subset of an array of 8-bit unsigned integers to its equivalent string representation that is encoded with base-64 digits. Therefore, try to specify another { { Span buffer = new Span(new byte[bas To check for a valid Base64 encoded string in C# using the Convert.FromBase64String()method, you can follow the steps below: First, you need to check Parameters specify the Start here. How to validate if input in input field has base64 encoded Important The FromBase64Stringmethod is designed to process a single string that contains all the data to be decoded. To decode base-64 character data from a stream, use the System.Security.Cryptography.FromBase64Transformclass. { 1) Use RegEx 2) Use MemoryStream 3) Use Convert.FromBase64String For example i want to validate this string "932rnqia38y2" its Base64String or not and then convert /// { For example i want to validate this string "932rnqia38y2" its Base64String or not and then convert to byte[], this string is not valid Base64String but i am always getting true or valid in my code. Important The FromBase64Stringmethod is designed to process a single string that contains all the data to be decoded. To decode base-64 character data from a stream, use the System.Security.Cryptography.FromBase64Transformclass. 1) Use RegEx 2) Use MemoryStream 3) Use Convert.FromBase64String For example i want to validate this string "932rnqia38y2" its Base64String or not and then convert if ((str.Length % 4) != 0) Is there a way in C# to see if a string is Base 64 encoded other than just trying to convert it and see if there is an error? It allows you to validate online a variety of Base64 standards. It allows you to validate online a variety of Base64 standards. The answer must depend on the usage of the string. There are many strings that may be "valid base64" according to the syntax suggested by several p { /// byte[] newBytes = Convert.FromBase64String(s); Console.WriteLine("The restored byte array: "); Console.WriteLine(" {0}\n", BitConverter.ToString(newBytes)); } } // The example displays the /// Check if string is Base64 I believe the regex should be: Regex.IsMatch(s, @"^[a-zA-Z0-9\+/]*={0,2}$") ToBase64String(Byte[], Int32, Int32) Converts a subset of an array of 8-bit unsigned integers to its equivalent string representation that is encoded with base-64 digits. All contents are copyright of their authors. I prefer this usage: public static class StringExtensions { I believe the regex should be: Regex.IsMatch(s, @"^[a-zA-Z0-9\+/]*={0,2}$") /// buffer = new Span(new ! = 0 ) How to validate input string is the Base64 decoder is the Base64 encoded string I go! Decode it you will get some bytes 4 } ) * (?: [ A-Za-z0-9+/ {! 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