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How do you create a new DataTable column expression using a column name and a variable?

Posted on 2006-07-20
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Last Modified: 2008-01-09
How do you create a new DataTable column expression using a columnName * variableName?

The following gives creates a new column, and an expression of MyColumn * (a fixed value)

       ' Create the new column.
        Dim MyNewColumn As New DataColumn
        MyNewColumn.ColumnName = "MyColumnName"
        MyNewColumn.Expression = "AnotherColumnName * 7"

        ' Add column to DataTable
        Me.MyDataSet.MyDataTable.Columns.Add(MyNewColumn)
     
In the above example, I am after the 7 being a variable, not a predetermined fixed value.
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Question by:IvanHowarth
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4 Comments
 
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Expert Comment

by:Nandakumar Sakthivel
ID: 17145585
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Accepted Solution

by:
arif_eqbal earned 500 total points
ID: 17145718
Dim i As Integer = 7
MyNewColumn.Expression = "AnotherColumnName * " & i


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LVL 6

Expert Comment

by:Nandakumar Sakthivel
ID: 17145758

Try this.,

 Dim x As Integer = 9  // assign the value that you want to multiply with the column here

Dim ds As New DataSet
Dim dt As New DataTable
Dim dr As DataRow

Dim column1 As New DataColumn
column1.ColumnName = "Number"
column1.DataType = GetType(Integer)
dt.Columns.Add(column1)

Dim column2 As New DataColumn
column2.ColumnName = "MinValue"
column2.DataType = GetType(Integer)
dt.Columns.Add(column2)

Dim column3 As New DataColumn
column3.ColumnName = "TotalValue"
column3.DataType = GetType(Integer)
column3.Expression = String.Format("Number * {0}", x)
dt.Columns.Add(column3)

dr = dt.NewRow
dr.item(0) = 5
dr.item(1) = 10
dt.Rows.Add(dr)

dr = dt.NewRow
dr.item(0) = 20
dr.item(1) = 30
dt.Rows.Add(dr)

Thanks,
Nanda
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Author Comment

by:IvanHowarth
ID: 17145772
arif_eqbal  answer was exactly what I needed.

Thanks both anyway.
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