private void Spreadsheet_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
if ("Text" == e.PropertyName) //checks if Cell.Text property was changed
{
string oldValue = ((Cell)sender).Value; //make a copy of the value of the old string for undo methods
ICmd temp = new RestoreText((Cell)sender, oldValue);
AddUndo(temp);
if (((Cell)sender).Text.IndexOf('=') == 0) //must evaluate if it's a formula
{
//remove cell from every hashset in dependency table to update the dependency table after formula evaluation
foreach (KeyValuePair <Cell, HashSet <Cell> > p in dependencies)
{
dependencies[p.Key].Remove((Cell)sender);
}
string formula = ((Cell)sender).Text.Replace("=", "");
var tree = new ExpTree(formula); //put the formula in tree for evaluation
string[] variables = tree.GetVars(); //get the variables from the tree
if (checkValidFormulaVariables(variables) && !checkSelfReference(((Cell)sender), variables)) //check if variables are in valid format
{
foreach (string s in variables)
{
double value = getCorrespondingCellValue(s); //get the individual variable value
tree.SetVar(s, value); //set the variable so the tree can evaluate the expression
updateDependencyTable((Cell)sender, s);
}
double finalValue = tree.Eval(); //returns the final result of formula evaluation
((Cell)sender).Value = finalValue.ToString();
}
else if (!checkValidFormulaVariables(variables)) //variables not in valid format
{
tree.ClearVariables(); //delete bad variables
((Cell)sender).Text = "!(invalid entry)";
}
else
{
tree.ClearVariables();
((Cell)sender).Text = "!(self reference)";
}
}
else //just a constant value or some string was entered
{
//check if any cells depend on the cell where value was changed and update them
if (dependencies.ContainsKey((Cell)sender) && dependencies[(Cell)sender].Count > 0)
{
foreach (Cell cell in dependencies[(Cell)sender])
{
//Re-evaluate the formulas of each cell depending on the changed cell
string formula = cell.Text.Replace("=", "");
var tree = new ExpTree(formula);
string[] vars = tree.GetVars();
if (checkValidFormulaVariables(vars)) //check if variables are in valid format
{
foreach (string v in vars)
{
Cell check = getCorrespondingCell(v);
double varValue = 0.0;
if (check == ((Cell)sender)) //check if the variable is the cell being changed
{
double.TryParse(((Cell)sender).Text, out varValue); //set value of that variable to the newly changed value
}
else
{
varValue = getCorrespondingCellValue(v);
}
tree.SetVar(v, varValue);
}
double finalValue = tree.Eval(); //returns the final result of formula evaluation
cell.Value = finalValue.ToString();
}
else
{
cell.Text = "!(invalid entry)";
}
}
}
((Cell)sender).Value = ((Cell)sender).Text; //set the value of the cell
}
}
if (CellPropertyChanged != null) //does the event have subscribers?
{
CellPropertyChanged(sender, e);
}
}