When you create an expression, use the ColumnName property to refer to columns.
This is the method you would use to count the number of transactions completed by a particular salesperson, as shown in this Visual Basic code: DataSet1.Tables("Orders").Columns("OrderCount").Expression = "Count(OrderID)" A simple example is to count the number of rows returned in the set. Similar to a calculated value, an aggregate performs an operation based on the complete set of rows in the DataTable.
STIMULSOFT CALCULATED COLUMN WITH AGGREGATE FUNCTION CODE
Because tax rates vary from region to region, it would be impossible to put a single tax rate in a column instead, the value is calculated using the Expression property, as shown in the Visual Basic code in the following section:ĭataSet1.Tables("Products").Columns("tax").Expression = "UnitPrice * 0.086"Ī second use is to create an aggregate column. For example, to calculate a tax value, the unit price is multiplied by a tax rate of a specific region. One use of the Expression property is to create calculated columns. TotalColumn.DataType = ("System.Decimal") TaxColumn.DataType = ("System.Decimal") ĭataColumn totalColumn = new DataColumn() Create the second, calculated, column. PriceColumn.DataType = ("System.Decimal") private void CalcColumns()ĭataColumn priceColumn = new DataColumn()
The resulting table is displayed in a DataGrid control. The second and third columns contain expressions the second calculates tax using a variable tax rate, and the third adds the result of the calculation to the value of the first column. The following example creates three columns in a DataTable. This includes expressions that evaluate to Char. When you use the LEN function or the TRIM function, the expression does not evaluate to a string.
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