CODEWITHSUNDEEP
c#.netstrongly-typed-dataset
user501211
user501211

Reputation: 465

DataSet Expression Column Re-Evaluation

I have a strongly typed data set that contains a readonly column calculated by its expression property. The calculated column is a totalAmountDue and the expression is ( totalAmountBilledColumn - totalAmountPaidColumn ). The problem is I can't get the calculated column to re-evaluate when either of the two calculating columns are changed.

Does anyone know how to force the data set to re-evaluate columns with expressions?

Thanks.

Upvotes: 1

Views: 2831

Answers (1)

Sheraz
Sheraz

Reputation: 2217

Just came across this. Funny thing about expressions is that they don't evaluate until row is added to table. Once a row is added to table, It will work. Here is an example.

        DataTable table = new DataTable();
        table.Columns.Add("debit", typeof (double)).DefaultValue = 0;
        table.Columns.Add("credit", typeof(double)).DefaultValue = 0;
        table.Columns.Add("net", typeof(double),"debit - credit");

        DataRow row = table.NewRow();

        Console.WriteLine("First: {0}",row["net"]); // won't work
        row["debit"] = 500;
        Console.WriteLine("Sec: {0}", row["net"]); // won't work
        row["credit"] = 0;
        Console.WriteLine("Thr: {0}", row["net"]); // won't work

        table.Rows.Add(row);
        Console.WriteLine(row["net"]); // works

Upvotes: 3

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