private void UpdateCellValue(ref SpreadsheetCell cell)
{
var mainTree = new ExpTree(); // Initializes a new expression tree to build the cell's expression
ErrType Error = ErrType.None;
if (cell.Text != "" && cell.Text[0] != '=') // not an expression, simply a text value
{
cellArr[cell.RowIndex, cell.ColumnIndex] = new Cell(cell, cell.Text);
add_remove(cell, mainTree, true);
}
else
{
if (cell.Text != "")
mainTree.Expression = cell.Text.Substring(1).Replace(" ", ""); // Build the expression tree with the cell's text (minus the '=') :: Also ignores whitespaces
else
mainTree.Expression = cell.Text;
add_remove(cell, mainTree, true); // Removes all variables cooresponding to the old tree
cell.VarList = GetVarNames(cell.Text); // Will Return all found variables in the new expression
Error = add_remove(cell, mainTree, false);
if (Error != ErrType.None) // Notifies the UI that there is an error in one of the cells that the expression references
{
return; // Exits the function before executing anything else, error display has already been taken care of at this point
}
try
{
cellArr[cell.RowIndex, cell.ColumnIndex] = new Cell(cell, mainTree.Eval().ToString()); // Attempts to evaluate the expression, placing it into a new cell
}
catch (DivideByZeroException) // User tried to divide by zero
{
CheckErr(cell, ErrType.DivZero, CellToString(cell));
UpdateErrorReferecedBy(cell, ErrType.DivZero, CellToString(cell));
return;
}
catch (NullReferenceException) // Input not regonized / invalid expression
{
if (cell.Text == "")
{
cellArr[cell.RowIndex, cell.ColumnIndex] = new Cell(cell, ""); // if the cell was deleted or reset, this will set the cell to an empty value (caught by expression tree as null)
}
else
{
CheckErr(cell, ErrType.InvExp, CellToString(cell));
UpdateErrorReferecedBy(cell, ErrType.InvExp, CellToString(cell)); // Notifies UI that an invalid expression has been entered
return;
}
}
}
cellArr[cell.RowIndex, cell.ColumnIndex].PropertyChanged += detect_PropertyChanged; // Reassigns the the detect_property function to the cell's delegate
CellPropertyChanged(cellArr[cell.RowIndex, cell.ColumnIndex], new PropertyChangedEventArgs("Value")); // fires the event that notifies the GUI of a change
UpdateReferencedBy(cell); // Updates all cells that reference this cell
}
