System.IO.TextReader.ReadAsync C# (CSharp) Method

        public virtual Task<int> ReadAsync(char[] buffer, int index, int count)
        {
            if (buffer == null)
            {
                throw new ArgumentNullException(nameof(buffer), SR.ArgumentNull_Buffer);
            }
            if (index < 0 || count < 0)
            {
                throw new ArgumentOutOfRangeException((index < 0 ? nameof(index): nameof(count)), SR.ArgumentOutOfRange_NeedNonNegNum);
            }
            if (buffer.Length - index < count)
            {
                throw new ArgumentException(SR.Argument_InvalidOffLen);
            }

            return ReadAsyncInternal(buffer, index, count);
        }

 public override Task <int> ReadAsync(char[] buffer, int index, int count)
 {
     lock (this) {
         return(reader.ReadAsync(buffer, index, count));
     }
 }