/// <summary>
/// This method will decide what course of action will need to be taken to
/// re-evaluate the odified expression.
/// </summary>
/// <param name="targetCell"></param>
private void HandleCellExpressionChange(SubCell targetCell)
{
string text = targetCell.Text;
/*EVALTUATE EXPRESSION*/
if (text.Length == 0)
{
targetCell.SetValue("");
}
else if (text[0] != '=')
{
//just set text as normal
targetCell.SetValue(targetCell.Text);
}
else //text.StartsWith("=") therefore, has cell ref
{
bool result;
try
{
EvaluateExpression(targetCell); //try to evaluate expression
}
catch
{
targetCell.SetValue("#REF!"); //set the value to empty string
}
result = VerifyNoCircleRef(targetCell);
if (result == true)
{
targetCell.SetValue("#CIRC REF!"); //set the value to empty string
}
}
}
/// <summary>
/// evaluate the the expression of the target cell. Find and set the value of each variable in the expression,
/// then set the target cells dependencies. Finally, set the value of the target cell to the result of the
/// evaluated expression tree.
/// </summary>
/// <param name="targetCell"></param>
private void EvaluateExpression(SubCell targetCell)
{
string targetExpression = targetCell.Text.Substring(1); //grab entire expression except "="
ExpressionTree expressionTree = new ExpressionTree(targetExpression); //create expression tree
try
{
if (expressionTree.Variables.Count == 1)
{
string variable = expressionTree.Variables.First();
int[] index = ConvertNameToLocation(variable);
SubCell dependentCell = GetCell(index[0], index[1]); //get cell at name location
if (dependencies.ContainsKey(targetCell) == false)
{
dependencies.Add(targetCell, new HashSet <SubCell>()); //create dependency Cell entry
}
dependencies[targetCell].Add(dependentCell); //add dependent cell hash value at key entry
if (dependentCell.Value == dependentCell.Text)
{
targetCell.SetValue(dependentCell.Text);
}
if (VerifyNoCircleRef(targetCell))
{
return;
}
}
else
{
foreach (string variable in expressionTree.Variables)
{
int[] index = ConvertNameToLocation(variable);
SubCell dependentCell = GetCell(index[0], index[1]); //get cell at name location
if (dependencies.ContainsKey(targetCell) == false)
{
dependencies.Add(targetCell, new HashSet <SubCell>()); //create dependency Cell entry
}
dependencies[targetCell].Add(dependentCell); //add dependent cell hash value at key entry
//if the dependent cell value is a constant (double)
double result;
if (double.TryParse(dependentCell.Value, out result))
{
expressionTree.SetVariable(variable, result);
}
}
//evaluate the expression tree, and set target cell value
targetCell.SetValue(expressionTree.Evaluate().ToString());
}
}
catch
{
throw; //throw the exception to HandleCellExpressionChange()
}
}
