Skip to main content

c# - How to create a DataTable with distinct rows from a DataView

Create a DataTable with distinct rows from a DataView
The DataView is a customized view of a DataTable for sorting, filtering, searching, editing, and navigation. The DataView does not store data. When the asp.net developer changes the DataView's data that will affect the DataTable. But when they change the DataTable's data that will affect all associated DataViews. The DataView is much like a database view.

The DataTable class represents one table of in-memory data. The DataTable is a central object in the ADO.NET library. The DataSet and DataView objects use DataTable.The following asp.net c# tutorial code demonstrates how we can create a DataTable with distinct rows from a DataView. Here we used the DataView class ToTable() method’s specified overload to create a DataTable with distinct rows from a specified DataView instance.

The DataView class ToTable() method creates and returns a new DataTable based on rows in an existing DataView. In the DataView class ToTable() method’s specified overload we passed a Boolean value that indicates whether the returned DataTable contains rows that have distinct values for all its columns or not.

The default value of this parameter is false. If this parameter value is set to true then the returned DataTable contains rows that have distinct values for all its columns. We also pass the column names to this method overload to distinct the rows based on them while creating the new DataTable.

The DataView ToTable() method returns a new DataTable instance that contains the requested rows and columns.The asp.net developers can use the overloaded version of the ToTable() method when they want to retrieve distinct values in a subset of available columns, specifying a new name for the returned DataTable.
DataTableFromADataViewWithDistinctValues.aspx 

<%@ Page Language="C#" AutoEventWireup="true" %>
<%@ Import Namespace="System.Data" %>

<!DOCTYPE html>
<script runat="server">
    protected void Button1_Click(object sender, System.EventArgs e)
    {
        DataTable dt = new DataTable();
        dt.TableName = "Books";

        DataColumn dc1 = new DataColumn();
        dc1.ColumnName = "BookID";
        dc1.DataType = typeof(int);
        dc1.AllowDBNull = false;
        dc1.Unique = true;

        DataColumn dc2 = new DataColumn();
        dc2.ColumnName = "Category";
        dc2.DataType = typeof(string);

        DataColumn dc3 = new DataColumn();
        dc3.ColumnName = "BookName";
        dc3.DataType = typeof(string);

        DataColumn dc4 = new DataColumn();
        dc4.ColumnName = "Author";
        dc4.DataType = typeof(string);

        dt.Columns.AddRange(new DataColumn[] { dc1, dc2, dc3, dc4 });

        dt.Rows.Add(new object[] { 1, "Flash", "Papervision3D Essentials", "Jeff Winder, Paul Tondeur" });
        dt.Rows.Add(new object[] { 2, "JBoss", "jBPM Developer Guide", "Mauricio Salatino" });
        dt.Rows.Add(new object[] { 3, "Flash", "Flash Multiplayer Virtual Worlds", "Makzan" });
        dt.Rows.Add(new object[] { 4, "Flash", "Papervision3D Essentials", "Jeff Winder, Paul Tondeur" });
        dt.AcceptChanges();

        Label1.Text = "Source DataTable: " + dt.TableName;
        GridView1.DataSource = dt.DefaultView;
        GridView1.DataBind();

        //this line create a new DataView
        DataView dView = new DataView(dt);
        dView.RowFilter = "Category = 'Flash'";

        Label2.Text = "Here we create a new DataView<br />" +
                      "and set the RowFilter (Category = 'Flash')";

        GridView2.DataSource = dView;
        GridView2.DataBind();

        //this line create a new DataTable from DataView
        DataTable dt2 = dView.ToTable(false, "BookName", "Author");

        Label3.Text = "Here we create a new DataTable from DataView";

        GridView3.DataSource = dt2;
        GridView3.DataBind();

        //this line create a new DataTable from DataView with distinct values
        DataTable dt3 = dView.ToTable(true, "BookName", "Author");

        Label4.Text = "Here we create a new DataTable from DataView with distinct values";

        GridView4.DataSource = dt3;
        GridView4.DataBind();
    }
</script>

<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
    <title>How to create a new DataTable from a DataView with distinct values (rows) in ado.net</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <h2 style="color:DarkBlue; font-style:italic;">
            How to create a new DataTable from a
            <br /> DataView with distinct values (rows) in ado.net
        </h2>
        <hr width="450" align="left" color="CornFlowerBlue" />
        <asp:Label
             ID="Label1"
             runat="server"
             Font-Size="Large"
             ForeColor="DodgerBlue"
             Font-Italic="true"
             >
        </asp:Label>
        <asp:GridView 
            ID="GridView1"
            runat="server"
            BorderColor="Snow"
            ForeColor="Snow"
            Width="750"
            Font-Names="Courier"
            >
            <HeaderStyle BackColor="HotPink" Height="30" />
            <RowStyle BackColor="OliveDrab" />
            <AlternatingRowStyle BackColor="DarkOliveGreen" />
        </asp:GridView>
        <asp:Label
             ID="Label2"
             runat="server"
             Font-Size="Large"
             ForeColor="DodgerBlue"
             Font-Italic="true"
             >
        </asp:Label>
        <asp:GridView 
            ID="GridView2"
            runat="server"
            BorderColor="Snow"
            ForeColor="Snow"
            Width="750"
            Font-Names="Courier"
            >
            <HeaderStyle BackColor="HotPink" Height="30" />
            <RowStyle BackColor="OliveDrab" />
            <AlternatingRowStyle BackColor="DarkOliveGreen" />
        </asp:GridView>
        <asp:Label
             ID="Label3"
             runat="server"
             Font-Size="Large"
             ForeColor="DodgerBlue"
             Font-Italic="true"
             >
        </asp:Label>
        <asp:GridView 
            ID="GridView3"
            runat="server"
            BorderColor="Snow"
            ForeColor="Snow"
            Width="750"
            Font-Names="Courier"
            >
            <HeaderStyle BackColor="HotPink" Height="30" />
            <RowStyle BackColor="OliveDrab" />
            <AlternatingRowStyle BackColor="DarkOliveGreen" />
        </asp:GridView>
        <asp:Label
             ID="Label4"
             runat="server"
             Font-Size="Large"
             ForeColor="DodgerBlue"
             Font-Italic="true"
             >
        </asp:Label>
        <asp:GridView 
            ID="GridView4"
            runat="server"
            BorderColor="Snow"
            ForeColor="Snow"
            Width="750"
            Font-Names="Courier"
            >
            <HeaderStyle BackColor="HotPink" Height="30" />
            <RowStyle BackColor="OliveDrab" />
            <AlternatingRowStyle BackColor="DarkOliveGreen" />
        </asp:GridView>
        <asp:Button 
            ID="Button1"
            runat="server"
            OnClick="Button1_Click"
            Text="Populate GridView"
            Height="45"
            Font-Bold="true"
            ForeColor="DodgerBlue"
            />
    </div>
    </form>
</body>
</html>
Labels:

Popular posts from this blog

Restricting Jetpack Compose TextField to Numeric Input Only

Jetpack Compose has revolutionized Android development with its declarative approach, enabling developers to build modern, responsive UIs more efficiently. Among the many components provided by Compose, TextField is a critical building block for user input. However, ensuring that a TextField accepts only numeric input can pose challenges, especially when considering edge cases like empty fields, invalid characters, or localization nuances. In this blog post, we'll explore how to restrict a Jetpack Compose TextField to numeric input only, discussing both basic and advanced implementations. Why Restricting Input Matters Restricting user input to numeric values is a common requirement in apps dealing with forms, payment entries, age verifications, or any data where only numbers are valid. Properly validating input at the UI level enhances user experience, reduces backend validation overhead, and minimizes errors during data processing. Compose provides the flexibility to implement ...
Read more

jetpack compose - TextField remove underline

Compose TextField Remove Underline The TextField is the text input widget of android jetpack compose library. TextField is an equivalent widget of the android view system’s EditText widget. TextField is used to enter and modify text. The following jetpack compose tutorial will demonstrate to us how we can remove (actually hide) the underline from a TextField widget in an android application. We have to apply a simple trick to remove (hide) the underline from the TextField. The TextField constructor’s ‘colors’ argument allows us to set or change colors for TextField’s various components such as text color, cursor color, label color, error color, background color, focused and unfocused indicator color, etc. Jetpack developers can pass a TextFieldDefaults.textFieldColors() function with arguments value for the TextField ‘colors’ argument. There are many arguments for this ‘TextFieldDefaults.textFieldColors()’function such as textColor, disabledTextColor, backgroundColor, cursorC...
Read more

jetpack compose - Image clickable

Compose Image Clickable The Image widget allows android developers to display an image object to the app user interface using the jetpack compose library. Android app developers can show image objects to the Image widget from various sources such as painter resources, vector resources, bitmap, etc. Image is a very essential component of the jetpack compose library. Android app developers can change many properties of an Image widget by its modifiers such as size, shape, etc. We also can specify the Image object scaling algorithm, content description, etc. But how can we set a click event to an Image widget in a jetpack compose application? There is no built-in property/parameter/argument to set up an onClick event directly to the Image widget. This android application development tutorial will demonstrate to us how we can add a click event to the Image widget and make it clickable. Click event of a widget allow app users to execute a task such as showing a toast message by cli...
Read more