Реализовать метод, возвращаемый строку

void S1(string s)
{
    //...
}
 
MessageBox.Show(S1("123"));

class Int32
{
    public int? TryParse(string s)
}

class Int32
{
    public KeyValuePair<bool,Int32> TryParse(string s)
}

private void MeasureChild (
  ref IItemContainerGenerator generator,
  ref IContainItemStorage itemStorageProvider,
  ref object parentItem,
  ref bool hasUniformOrAverageContainerSizeBeenSet,
  ref double computedUniformOrAverageContainerSize,
  ref bool computedAreContainersUniformlySized,
  ref IList items,
  ref object item,
  ref IList children,
  ref int childIndex,
  ref bool visualOrderChanged,
  ref bool isHorizontal,
  ref Size childConstraint,
  ref Rect viewport,
  ref VirtualizationCacheLength cacheSize,
  ref VirtualizationCacheLengthUnit cacheUnit,
  ref bool foundFirstItemInViewport,
  ref double firstItemInViewportOffset,
  ref Size stackPixelSize,
  ref Size stackPixelSizeInViewport,
  ref Size stackPixelSizeInCacheBeforeViewport,
  ref Size stackPixelSizeInCacheAfterViewport,
  ref Size stackLogicalSize,
  ref Size stackLogicalSizeInViewport,
  ref Size stackLogicalSizeInCacheBeforeViewport,
  ref Size stackLogicalSizeInCacheAfterViewport,
  ref bool mustDisableVirtualization,
  bool isBeforeFirstItem,
  bool isAfterFirstItem,
  bool isAfterLastItem,
  bool skipActualMeasure,
  bool skipGeneration,
  ref bool hasBringIntoViewContainerBeenMeasured,
  ref bool hasVirtualizingChildren)