反编译源码StringBuilder.AppendLine
/// <summary>
/// Appends the default line terminator to the end of the current <see cref="T:System.Text.StringBuilder"/> object.
///
/// </summary>
///
/// <returns>
/// A reference to this instance after the append operation has completed.
///
/// </returns>
/// <exception cref="T:System.ArgumentOutOfRangeException">Enlarging the value of this instance would exceed <see cref="P:System.Text.StringBuilder.MaxCapacity"/>.
/// </exception><filterpriority>1</filterpriority>
[ComVisible(false)]
[__DynamicallyInvokable]
public StringBuilder AppendLine()
{
return this.Append(Environment.NewLine);
}