How to get distinct values from a datatable in strongly typed dataset

Question

I am using strongly typed dataset and have many tables in that..

The problem is now i want to filter data from

GetData()

function which has a query like

select * from table_name

How can i filter a particular table and distinct values from it. Also if i try to filter it return all column but rest have null values except the one i asked, so i cannot assign it as a datasource to a datagrid or combobox

How can i do this..

Answer 1

Your question is not very clear. What I have understood is, you have multiple tables coming in a dataset. Now you want to filter based about Table Name. If you are returning multiple tables in dataset by writing multiple select queries in a single stored procedure, then there is no way you could name the tables in sql. You have to access it by hard coded way. Another way could be you could add a table at 0th position and in that table add the name of the table and position that it would be in DataSet while returning the query. So the first query in your stored procedure would return a table which has mapping between name of the table and postion they are in DataSet. Now GetData() function would become very easy.

function DataTable GetData(string tableName)
{
  //Supposing 0th table is mapping table with 2 columns, One contains Name and another   position
   var pos = ds.Tables[0].where(x => x[0] == tableName).Select(x => x[1]).firstOrDefault();
   var table = ds.Tables[pos];
   return table;
}

Answer 2

How about the Select() method of the DataTable?

DataRow[] filtered = someDataSet.SomeDataTable.Select("Status = 'Active'");

Edit:
Updated code sample following OP's comment

using System.Linq;
...
DataRow[] rows = someDataSet.SomeDataTable.Select("Status = 'Active'");
string[] columnValues = row.Select(x => x["SomeColumnName"].ToString());

Note, the two Select() methods are different. The first is a DataTable method that filters rows. The second is a linq extension method that is transforming an array of rows into an array of strings.

Answer 3

As I understood your question, I did something quick to try to help, the code can be improved and must be, how I said I did it fast.

Public Module DataSetExtensions
    <Runtime.CompilerServices.Extension()>
    Public Function [Select](ds As DataSet, table As String, ParamArray campos() As String) As DataTable
        Dim dt As New DataTable
        Dim sourceTable = (From t As DataTable In ds.Tables _
            Where t.TableName = table).SingleOrDefault

        Dim columnas = From c As DataColumn In sourceTable.Columns Where campos.Contains(c.ColumnName)

        columnas.ToList.ForEach(Sub(c) dt.Columns.Add(c.ColumnName))

        For Each row As DataRow In sourceTable.Rows
            Dim newRow As DataRow = dt.NewRow
            For Each col As DataColumn In sourceTable.Columns
                If columnas.Contains(col) Then
                    newRow(col.ColumnName) = row(col)
                End If
            Next
            dt.Rows.Add(newRow)
        Next

        Return dt
    End Function

    <Runtime.CompilerServices.Extension()>
    Public Function [Select](table As DataTable, ParamArray campos() As String) As DataTable
        Dim dt As New DataTable

        Dim columnas = From c As DataColumn In table.Columns Where campos.Contains(c.ColumnName)

        columnas.ToList.ForEach(Sub(c) dt.Columns.Add(c.ColumnName))

        For Each row As DataRow In table.Rows
            Dim newRow As DataRow = dt.NewRow
            For Each col As DataColumn In table.Columns
                If columnas.Contains(col) Then
                    newRow(col.ColumnName) = row(col)
                End If
            Next
            dt.Rows.Add(newRow)
        Next

        Return dt
    End Function
End Module

And the call something like this

Using ds As New DataSet1()
    Using ta As New DataSet1TableAdapters.BCR_SOLICITUDTableAdapter()
        ta.Fill(ds.BCR_SOLICITUD)
        Dim dt As DataTable
        ' First extended method
        dt = ds.Select("BCR_SOLICITUD", "Numero", "Estado", "Descripción")
        ' Second extended method
        dt = ds.BCR_SOLICITUD.Select("Numero","Estado", "Descripción")
        'Code here
        dt.Dispose
        dt=Nothing
    End Using
End Using

You could use using in DataTable, but this is not the topic. I hope it help you.