StringReader.ReadAsync StringReader.ReadAsync StringReader.ReadAsync StringReader.ReadAsync Method

Definition

Overloads

ReadAsync(Memory<Char>, CancellationToken) ReadAsync(Memory<Char>, CancellationToken)
ReadAsync(Char[], Int32, Int32) ReadAsync(Char[], Int32, Int32) ReadAsync(Char[], Int32, Int32) ReadAsync(Char[], Int32, Int32)

Reads a specified maximum number of characters from the current string asynchronously and writes the data to a buffer, beginning at the specified index.

ReadAsync(Memory<Char>, CancellationToken) ReadAsync(Memory<Char>, CancellationToken)

public override System.Threading.Tasks.ValueTask<int> ReadAsync (Memory<char> buffer, System.Threading.CancellationToken cancellationToken = null);
override this.ReadAsync : Memory<char> * System.Threading.CancellationToken -> System.Threading.Tasks.ValueTask<int>

Parameters

buffer
Memory<Char>

Returns

ReadAsync(Char[], Int32, Int32) ReadAsync(Char[], Int32, Int32) ReadAsync(Char[], Int32, Int32) ReadAsync(Char[], Int32, Int32)

Reads a specified maximum number of characters from the current string asynchronously and writes the data to a buffer, beginning at the specified index.

public:
 override System::Threading::Tasks::Task<int> ^ ReadAsync(cli::array <char> ^ buffer, int index, int count);
[System.Runtime.InteropServices.ComVisible(false)]
public override System.Threading.Tasks.Task<int> ReadAsync (char[] buffer, int index, int count);
override this.ReadAsync : char[] * int * int -> System.Threading.Tasks.Task<int>
Public Overrides Function ReadAsync (buffer As Char(), index As Integer, count As Integer) As Task(Of Integer)

Parameters

buffer
Char[]

When this method returns, contains the specified character array with the values between index and (index + count - 1) replaced by the characters read from the current source.

index
Int32 Int32 Int32 Int32

The position in buffer at which to begin writing.

count
Int32 Int32 Int32 Int32

The maximum number of characters to read. If the end of the string is reached before the specified number of characters is written into the buffer, the method returns.

Returns

A task that represents the asynchronous read operation. The value of the TResult parameter contains the total number of bytes read into the buffer. The result value can be less than the number of bytes requested if the number of bytes currently available is less than the requested number, or it can be 0 (zero) if the end of the string has been reached.

Exceptions

The sum of index and count is larger than the buffer length.

Examples

The following example shows how to read the first 23 characters of a string asynchronously.

using System;
using System.IO;

namespace ConsoleApplication
{
    class Program
    {
        static void Main(string[] args)
        {
            ReadCharacters();
        }

        static async void ReadCharacters()
        {
            string stringToRead = "Some characters to read but not all";
            char[] charsRead = new char[stringToRead.Length];

            using (StringReader reader = new StringReader(stringToRead))
            {
                await reader.ReadAsync(charsRead, 0, 23);
                Console.WriteLine(charsRead);
            }
        }
    }
}
// The example displays the following output:
// Some characters to read
//
Imports System.IO

Module Module1

    Sub Main()
        ReadCharacters()
    End Sub

    Async Sub ReadCharacters()
        Dim stringToRead = "Some characters to read but not all"
        Dim charsRead(stringToRead.Length) As Char

        Using reader As StringReader = New StringReader(stringToRead)
            Await reader.ReadAsync(charsRead, 0, 23)
            Console.WriteLine(charsRead)
        End Using
    End Sub

End Module
' The example displays the following output:
' Some characters to read
'

Remarks

The task completes after either the number of characters specified by the count parameter are read or the end of the string is reached.

Applies to