How to find values from SQLdatasource dataview

 DataView view = (DataView)dataSource.Select(new DataSourceSelectArguments());

DataTable groupsTable = view.ToTable();
String value;

foreach (DataRow dr in dt.Rows)
{
    // Do something here IE grab the value of the first column
    value = dr[0];
}

or

 DataView dv = (DataView)SqlDataSource1.Select(DataSourceSelectArguments.Empty);
    int reorderedProducts = (int)dv.Table.Rows[0][0];
    if (reorderedProducts > 0)
    {
        Label1.Text = "Number of products on reorder: " + reorderedProducts;
    }
    else
    {
        Label1.Text = "No products on reorder.";
    }

or

var view = (DataView)bindingSource1.DataSource;
DataTable productsTable = view.Table;

// Set RowStateFilter to display the current rows.
view.RowStateFilter = DataViewRowState.CurrentRows;

// Query the DataView for red colored products ordered by list price.
var productQuery = from DataRowView rowView in view
                   where rowView.Row.Field<string>("Color") == "Red"
                   orderby rowView.Row.Field<decimal>("ListPrice")
                   select new
                   {
                       Name = rowView.Row.Field<string>("Name"),
                       Color = rowView.Row.Field<string>("Color"),
                       Price = rowView.Row.Field<decimal>("ListPrice")
                   };

// Bind the query results to another DataGridView.
dataGridView2.DataSource = productQuery.ToList();

or

DataView custView = new DataView(custDS.Tables["Customers"], "",  
  "CompanyName, ContactName",  
  DataViewRowState.CurrentRows);  
  
DataRowView[] foundRows =
  custView.FindRows(new object[] {"The Cracker Box", "Liu Wong"});  
  
if (foundRows.Length == 0)  
  Console.WriteLine("No match found.");  
else  
  foreach (DataRowView myDRV in foundRows)  
    Console.WriteLine("{0}, {1}", myDRV["CompanyName"].ToString(),
      myDRV["ContactName"].ToString());  

ref:- https://learn.microsoft.com/en-us/dotnet/framework/data/adonet/querying-the-datarowview-collection-in-a-dataview

https://stackoverflow.com/questions/5516464/sqldatasource-select-how-do-i-use-this-asp-net

https://learn.microsoft.com/en-us/dotnet/api/system.web.ui.webcontrols.sqldatasource.select?view=netframework-4.8.1

https://learn.microsoft.com/en-us/dotnet/framework/data/adonet/dataset-datatable-dataview/finding-rows