DataTable::Compute Method (String^, String^)

 
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Computes the given expression on the current rows that pass the filter criteria.

Namespace:   System.Data
Assembly:  System.Data (in System.Data.dll)

public:
Object^ Compute(
	String^ expression,
	String^ filter
)

Parameters

expression
Type: System::String^

The expression to compute.

filter
Type: System::String^

The filter to limit the rows that evaluate in the expression.

Return Value

Type: System::Object^

An Object, set to the result of the computation. If the expression evaluates to null, the return value will be DBNull::Value.

The expression parameter requires an aggregate function. For example, the following is a legal expression:

Count(Quantity)

But this expression is not:

Sum (Quantity * UnitPrice)

If you must perform an operation on two or more columns, you should create a DataColumn, set its Expression property to an appropriate expression, and use an aggregate expression on the resulting column. In that case, given a DataColumn with the name "total", and the Expression property set to this:

"Quantity * UnitPrice"

The expression argument for the Compute method would then be this:

Sum(total)

The second parameter, filter, determines which rows are used in the expression. For example, if the table contains a date column named "colDate", you could limit the rows with the following expression:

colDate > 1/1/99 AND colDate < 17/1/99

For rules on creating expressions for both parameters, see the DataColumn::Expression property.

The following example sums the values of a column named "Total", for the salesperson whose identification number is five.

No code example is currently available or this language may not be supported.

.NET Framework
Available since 1.1
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