private DataColumn AddColumnToDataTable(Expression expression)
{
DataColumn dc = null;
string newColName = expression.ToString();
if (!_dt.Columns.Contains(newColName))
{
dc = _dt.Columns.Add(newColName, typeof(double));
dc.ExtendedProperties[VBCommon.Globals.OPERATION] = true;
foreach (string var in expression.Variables)
{
DataColumn dc2 = _dt.Columns[var];
if (dc2.ExtendedProperties.ContainsKey(VBCommon.Globals.TRANSFORM))
{
dc.ExtendedProperties.Add(VBCommon.Globals.TRANSFORM, true);
break;
}
}
}
return dc;
}
/// <summary>
/// This function verifies that the expression contains a valid Operation and that the field(s) are included in the datatable
/// </summary>
/// <param name="expression">Expression to be verified</param>
private bool ExecuteExpression(Expression expression)
{
switch (expression.Operation)
{
case Globals.Operations.MAX :
MAXIMUM(expression);
break;
case Globals.Operations.MEAN:
MEAN(expression);
break;
case Globals.Operations.PROD:
PRODUCT(expression);
break;
case Globals.Operations.SUM:
SUM(expression);
break;
case Globals.Operations.MIN:
MINIMUM(expression);
break;
}
return true;
}
private bool VerifyExpression(Expression expression)
{
if (_dt == null)
return false;
foreach (string var in expression.Variables)
{
if (_dt.Columns.Contains(var) == false)
return false;
}
return true;
}
/// <summary>
/// Sum the values of all the fields in the expression
/// </summary>
/// <param name="expression"></param>
private void SUM(Expression expression)
{
string newColName = expression.ToString();
DataColumn dc = AddColumnToDataTable(expression);
if (dc != null)
{
for (int i = 0; i < _dt.Rows.Count; i++)
{
double sum = 0.0;
foreach (string var in expression.Variables)
{
sum += Convert.ToDouble(_dt.Rows[i][var]);
}
_dt.Rows[i][newColName] = sum;
}
}
}
public ExpressionExecution(DataTable dt, Expression[] expressions)
{
_dt = dt.Copy();
_expressions = expressions;
Init();
}
/// <summary>
/// Multiply the values of all the fields in the expression
/// </summary>
/// <param name="expression"></param>
private void PRODUCT(Expression expression)
{
string newColName = expression.ToString();
DataColumn dc = AddColumnToDataTable(expression);
if (dc != null)
{
for (int i = 0; i < _dt.Rows.Count; i++)
{
double product = 1.0;
foreach (string var in expression.Variables)
{
product = product * Convert.ToDouble(_dt.Rows[i][var]);
}
_dt.Rows[i][newColName] = product;
}
}
}
/// <summary>
/// Select the mininum values of all the fields in the expression
/// </summary>
/// <param name="expression"></param>
private void MINIMUM(Expression expression)
{
string newColName = expression.ToString();
DataColumn dc = AddColumnToDataTable(expression);
if (dc != null)
{
for (int i = 0; i < _dt.Rows.Count; i++)
{
double min = double.PositiveInfinity;
foreach (string var in expression.Variables)
{
double current = Convert.ToDouble(_dt.Rows[i][var]);
if (current < min)
min = current;
}
_dt.Rows[i][newColName] = min;
}
}
}
public Expression(Expression exp)
{
_operation = exp.Operation;
lstVariables = exp.Variables.ToList();
strExpressionString = exp.ExpressionString;
}
