Get DataTable rows with next and previous Button in ASP.Net using C# and VB.Net

Hi Awais,

Check this example. Now please take its reference and correct your code.

HTML

<table>
    <tr>
        <td>
            <h1><asp:Label ID="lblQuestion" runat="server" /></h1>
        </td>
    </tr>
    <tr>
        <td>
            <asp:RadioButtonList ID="rbtnOptions" runat="server">
            </asp:RadioButtonList>
        </td>
    </tr>
    <tr>
        <td>
            <asp:Button ID="btnNext" Text="Next" runat="server" OnClick="OnNext" Style="float: left;" />
            <asp:Button ID="btnPrevious" Text="Previous" runat="server" OnClick="OnPrevious" Style="float: right;" />
        </td>
    </tr>
</table>

Namespaces

C#

using System.Data;

VB.Net

Imports System.Data

Code

C#

private DataTable QuestionsTable
{
    get { return (DataTable)ViewState["Question"]; }
    set { ViewState["Question"] = value; }
}

private DataTable AnsweredTable
{
    get
    {
        if (ViewState["Answer"] == null)
        {
            DataTable dt = new DataTable();
            dt.Columns.Add("Question", typeof(string));
            dt.Columns.Add("Answered", typeof(int));
            ViewState["Answer"] = dt;
            return (DataTable)ViewState["Answer"];
        }
        else
        {
            return (DataTable)ViewState["Answer"];
        }
    }
    set { ViewState["Answer"] = value; }
}

private int QuestionIndex
{
    get { return (int)ViewState["QuestionIndex"]; }
    set { ViewState["QuestionIndex"] = value; }
}

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        QuestionsTable = PopulateQuestions();
        QuestionIndex = 0;
        EnableDisableNextPrevious();
        GetCurrentQuestion(QuestionIndex, QuestionsTable);
        btnPrevious.Enabled = false;
    }
}

protected void OnNext(object sender, EventArgs e)
{
    SetSelectedAnswer();
    QuestionIndex++;
    EnableDisableNextPrevious();
    GetCurrentQuestion(QuestionIndex, QuestionsTable);
    SetSelectedOption();
}

protected void OnPrevious(object sender, EventArgs e)
{
    SetSelectedAnswer();
    QuestionIndex--;
    EnableDisableNextPrevious();
    GetCurrentQuestion(QuestionIndex, QuestionsTable);
    SetSelectedOption();
}

private void SetSelectedAnswer()
{
    DataTable dt = AnsweredTable;
    DataRow[] drs = dt.Select("Question='" + lblQuestion.Text.Trim() + "'");
    if (drs.Length > 0)
    {
        drs[0]["Answered"] = rbtnOptions.SelectedItem != null ? int.Parse(rbtnOptions.SelectedItem.Value) : (object)DBNull.Value;
    }
    else
    {
        DataRow dr = dt.NewRow();
        dr["Question"] = lblQuestion.Text.Trim();
        dr["Answered"] = rbtnOptions.SelectedItem != null ? int.Parse(rbtnOptions.SelectedItem.Value) : (object)DBNull.Value;
        dt.Rows.Add(dr);
    }

    AnsweredTable = dt;
}

private void SetSelectedOption()
{
    DataRow[] dr = AnsweredTable.Select("Question='" + lblQuestion.Text.Trim() + "'");
    if (dr.Length > 0)
    {
        if (rbtnOptions.Items.FindByValue(dr[0]["Answered"].ToString()) != null)
        {
            rbtnOptions.Items.FindByValue(dr[0]["Answered"].ToString()).Selected = true;
        }
    }
}

private void EnableDisableNextPrevious()
{
    btnPrevious.Enabled = QuestionIndex == 0 ? false : true;
    btnNext.Enabled = QuestionIndex == QuestionsTable.Rows.Count - 1 ? false : true;
}

private DataTable PopulateQuestions()
{
    DataTable dt = new DataTable();
    dt.Columns.Add("QuestionID", typeof(int));
    dt.Columns.Add("QuestionStatement", typeof(string));
    dt.Columns.Add("QuestionAnswer", typeof(string));
    dt.Columns.Add("OptionA", typeof(string));
    dt.Columns.Add("OptionB", typeof(string));
    dt.Columns.Add("OptionC", typeof(string));
    dt.Columns.Add("OptionD", typeof(string));
    dt.Rows.Add(1, "What is an apple?", "Fruit", "Vegetable", "Hammond", "Fruit", "None");
    dt.Rows.Add(2, "What is an carrot?", "Vege.", "VegeVegetable", "Hammond", "Fruit", "None");
    dt.Rows.Add(3, "What is an egg?", "Chicken", "Vegetable", "Chicken", "Fruit", "None");
    dt.Rows.Add(4, "What is an box?", "Wooden", "Vegetable", "Hammond", "Wooden", "None");
    dt.Rows.Add(5, "What is an door?", "Steel", "Vegetable", "Hammond", "Fruit", "Steel");
    dt.Rows.Add(6, "What is a piano?", "Musical Device", "Vegetable", "Hammond", "Fruit", "Musical Device");

    return dt;
}

private void GetCurrentQuestion(int index, DataTable dtQuestions)
{
    DataRow row = dtQuestions.Rows[index];
    lblQuestion.Text = row["QuestionStatement"].ToString();
    List<ListItem> options = new List<ListItem>();
    options.AddRange(new ListItem[4] {
            new ListItem(row["OptionA"].ToString(), "0"),
            new ListItem(row["OptionB"].ToString(), "1"),
            new ListItem(row["OptionC"].ToString(), "2"),
            new ListItem(row["OptionD"].ToString(), "3")
        });
    rbtnOptions.Items.Clear();
    rbtnOptions.Items.AddRange(options.ToArray());
    rbtnOptions.DataBind();
}

VB.Net

Private Property QuestionsTable As DataTable
    Get
        Return CType(ViewState("Question"), DataTable)
    End Get
    Set(ByVal value As DataTable)
        ViewState("Question") = value
    End Set
End Property

Private Property AnsweredTable As DataTable
    Get
        If ViewState("Answer") Is Nothing Then
            Dim dt As DataTable = New DataTable()
            dt.Columns.Add("Question", GetType(String))
            dt.Columns.Add("Answered", GetType(Integer))
            ViewState("Answer") = dt
            Return CType(ViewState("Answer"), DataTable)
        Else
            Return CType(ViewState("Answer"), DataTable)
        End If
    End Get
    Set(ByVal value As DataTable)
        ViewState("Answer") = value
    End Set
End Property

Private Property QuestionIndex As Integer
    Get
        Return CInt(ViewState("QuestionIndex"))
    End Get
    Set(ByVal value As Integer)
        ViewState("QuestionIndex") = value
    End Set
End Property

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        QuestionsTable = PopulateQuestions()
        QuestionIndex = 0
        EnableDisableNextPrevious()
        GetCurrentQuestion(QuestionIndex, QuestionsTable)
        btnPrevious.Enabled = False
    End If
End Sub

Protected Sub OnNext(ByVal sender As Object, ByVal e As EventArgs)
    SetSelectedAnswer()
    QuestionIndex += 1
    EnableDisableNextPrevious()
    GetCurrentQuestion(QuestionIndex, QuestionsTable)
    SetSelectedOption()
End Sub

Protected Sub OnPrevious(ByVal sender As Object, ByVal e As EventArgs)
    SetSelectedAnswer()
    QuestionIndex -= 1
    EnableDisableNextPrevious()
    GetCurrentQuestion(QuestionIndex, QuestionsTable)
    SetSelectedOption()
End Sub

Private Sub SetSelectedAnswer()
    Dim dt As DataTable = AnsweredTable
    Dim drs As DataRow() = dt.Select("Question='" & lblQuestion.Text.Trim() & "'")
    If drs.Length > 0 Then
        drs(0)("Answered") = If(rbtnOptions.SelectedItem IsNot Nothing, Integer.Parse(rbtnOptions.SelectedItem.Value), CObj(DBNull.Value))
    Else
        Dim dr As DataRow = dt.NewRow()
        dr("Question") = lblQuestion.Text.Trim()
        dr("Answered") = If(rbtnOptions.SelectedItem IsNot Nothing, Integer.Parse(rbtnOptions.SelectedItem.Value), CObj(DBNull.Value))
        dt.Rows.Add(dr)
    End If

    AnsweredTable = dt
End Sub

Private Sub SetSelectedOption()
    Dim dr As DataRow() = AnsweredTable.Select("Question='" & lblQuestion.Text.Trim() & "'")
    If dr.Length > 0 Then
        If rbtnOptions.Items.FindByValue(dr(0)("Answered").ToString()) IsNot Nothing Then
            rbtnOptions.Items.FindByValue(dr(0)("Answered").ToString()).Selected = True
        End If
    End If
End Sub

Private Sub EnableDisableNextPrevious()
    btnPrevious.Enabled = If(QuestionIndex = 0, False, True)
    btnNext.Enabled = If(QuestionIndex = QuestionsTable.Rows.Count - 1, False, True)
End Sub

Private Function PopulateQuestions() As DataTable
    Dim dt As DataTable = New DataTable()
    dt.Columns.Add("QuestionID", GetType(Integer))
    dt.Columns.Add("QuestionStatement", GetType(String))
    dt.Columns.Add("QuestionAnswer", GetType(String))
    dt.Columns.Add("OptionA", GetType(String))
    dt.Columns.Add("OptionB", GetType(String))
    dt.Columns.Add("OptionC", GetType(String))
    dt.Columns.Add("OptionD", GetType(String))
    dt.Rows.Add(1, "What is an apple?", "Fruit", "Vegetable", "Hammond", "Fruit", "None")
    dt.Rows.Add(2, "What is an carrot?", "Vege.", "VegeVegetable", "Hammond", "Fruit", "None")
    dt.Rows.Add(3, "What is an egg?", "Chicken", "Vegetable", "Chicken", "Fruit", "None")
    dt.Rows.Add(4, "What is an box?", "Wooden", "Vegetable", "Hammond", "Wooden", "None")
    dt.Rows.Add(5, "What is an door?", "Steel", "Vegetable", "Hammond", "Fruit", "Steel")
    dt.Rows.Add(6, "What is a piano?", "Musical Device", "Vegetable", "Hammond", "Fruit", "Musical Device")
    Return dt
End Function

Private Sub GetCurrentQuestion(ByVal index As Integer, ByVal dtQuestions As DataTable)
    Dim row As DataRow = dtQuestions.Rows(index)
    lblQuestion.Text = row("QuestionStatement").ToString()
    Dim options As List(Of ListItem) = New List(Of ListItem)()
    options.AddRange(New ListItem(3) {
                        New ListItem(row("OptionA").ToString(), "0"),
                        New ListItem(row("OptionB").ToString(), "1"),
                        New ListItem(row("OptionC").ToString(), "2"),
                        New ListItem(row("OptionD").ToString(), "3")})
    rbtnOptions.Items.Clear()
    rbtnOptions.Items.AddRange(options.ToArray())
    rbtnOptions.DataBind()
End Sub

Screenshot