ASP.NET

path = TextBox3.Text

        s1 = "Provider=Microsoft.Jet.OLEDB.4.0;" & "Data Source=" + path + ";Extended Properties=""Excel 8.0;HDR=YES;"""

        Dim OLEcon As OleDb.OleDbConnection = New OleDb.OleDbConnection(s1)

        Dim OLEcmd As New OleDb.OleDbCommand
        Dim OLEda As New OleDb.OleDbDataAdapter
        Dim OLEdt As New DataTable
        Dim sql As String
        Dim resul As Boolean
        OLEcon.Close()

        Try
            OLEcon.Open()



            With OLEcmd
                .Connection = OLEcon
                .CommandText = "Select * from [data1$]"
            End With
            OLEda.SelectCommand = OLEcmd
            OLEda.Fill(OLEdt)

            For Each r As DataRow In OLEdt.Rows

I have a datatable like this

----------------------------
STID	NAME	DOB	SBCD
----------------------------
1001	XXX	DMY	AAAA
1001	XXX	DMY	BBBB
1001	XXX	DMY	CCCC
1001	XXX	DMY	DDDD
1002	YYY	DMY	AAAA
1002	YYY	DMY	BBBB
1002	YYY	DMY	CCCC
1003	ZZZ	DMY	AAAA
1003	ZZZ	DMY	BBBB
1003	ZZZ	DMY	CCCC
1003	ZZZ	DMY	DDDD
1003	ZZZ	DMY	EEEE

I want to convert this datatable into following format and bind it to gridview.

----------------------------------------------------------------------
| STID | NAME / DOB	| 	            SUBJECTS                 |
|------|----------------|--------------------------------------------|
|1001  | XXX		|	AAAA	BBBB	CCCC	DDDD         |
|      | DMY            |	                                     |
|------|----------------|--------------------------------------------|
|1002  | YYY   		|	AAAA	BBBB	CCCC                 |
|      | DMY            |                                            |
|------|----------------|--------------------------------------------|
|1003  | ZZZ         	|	AAAA	BBBB	CCCC	DDDD	EEEE |
|      | DOB            |                                            |
|------|----------------|--------------------------------------------|

what is major difference between blazor server app and asp.net mvc razor app?

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1 Post

gridview with dynamic dropdownlist control null exception
33 minutes ago|LINK|157.50.247.59

I have a GridView with template fields and one of the template field is a dropdownlist which is dynamically added into the gridview control. It's working properly on page load when I click the button control to the get the values from the template fields it will throw a null reference exception. Please correct my error, I am in pathetic situation. I attached the source code.

Regards

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false"
        OnRowCreated="GridView1_RowCreated">
        <Columns>
            <asp:TemplateField>
                <ItemTemplate>
                    <asp:Label ID="id" runat="server" Text='<%# Eval("RGNO") %>'></asp:Label>
                </ItemTemplate>
            </asp:TemplateField>
        </Columns>
        <Columns>
            <asp:TemplateField>
                <ItemTemplate>
                    <asp:Label ID="name" runat="server" Text='<%# Eval("NAME") %>'></asp:Label>
                </ItemTemplate>
            </asp:TemplateField>
        </Columns>
        <Columns>
            <asp:TemplateField>
                <ItemTemplate>
                    <asp:Label ID="lastname" runat="server" Text='<%# Eval("DOB") %>'></asp:Label>
                </ItemTemplate>
            </asp:TemplateField>
        </Columns>
        <Columns>
            <asp:TemplateField>
                <ItemTemplate>
                    <asp:PlaceHolder ID="PlaceHolder1" runat="server"></asp:PlaceHolder>
                </ItemTemplate>
            </asp:TemplateField>
        </Columns>
    </asp:GridView>

protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
            BindGridView();
    }

    protected void GridView1_RowCreated(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            DropDownList ddlResult = new DropDownList();
            ddlResult.ID = "ddlResult";
            ddlResult.Items.Insert(0, new ListItem("PASS", "0"));
            ddlResult.Items.Insert(1, new ListItem("FAIL", "1"));

            PlaceHolder p = (PlaceHolder)e.Row.FindControl("PlaceHolder1");
            p.Controls.Add(ddlResult);
        }
    }

    private void BindGridView()
    {
        GridView1.DataSource = CreateDataSource();
        GridView1.DataBind();
    }

    public DataTable CreateDataSource()
    {
        DataTable dt = new DataTable();
        DataRow dr;

        dt.Columns.Add(new DataColumn("RGNO", typeof(string)));
        dt.Columns.Add(new DataColumn("NAME", typeof(string)));
        dt.Columns.Add(new DataColumn("DOB", typeof(string)));

        dr = dt.NewRow();
        dr["RGNO"] = "1001";
        dr["NAME"] = "PRAKASH";
        dr["DOB"] = "10-10-2003";
        dt.Rows.Add(dr);
        return dt;
    }

    protected void Button1_Click(object sender, EventArgs e)
    {
        foreach (GridViewRow row in GridView1.Rows)
        {
            DropDownList dd1 = (DropDownList)row.FindControl("ddlResult");
            Response.Write(dd1.SelectedItem.Text);
        }
    }

This my aspx code
<table align="center">
        <tr valign="top">
            <td>
                <asp:DataList ID="gv1" runat="server" RepeatColumns="1" RepeatDirection="Horizontal">
                    <HeaderTemplate>
                        Our Tutors List</HeaderTemplate>
                    <ItemTemplate>
                        <table width="600px" border="2" align="center">
                            <tr align="center">
                                <td width="100%" valign="top" style="font-size: 15px">
                            Name: <%#DataBinder.Eval(Container.DataItem, "FirstName")%>  <%#DataBinder.Eval(Container.DataItem, "LastName")%>
                            <%--Mobile:        <%#DataBinder.Eval(Container.DataItem, "MobileNo")%>    
                               Email Id:     <%#DataBinder.Eval(Container.DataItem, "EmailId")%>    --%>
                                </td>
                            </tr>
                            <tr>
                                <td>
                               Qualification:    <%#DataBinder.Eval(Container.DataItem, "Qualification")%>            
                                  Experience:  <%#DataBinder.Eval(Container.DataItem, "Experience")%>
                                     
                                </td>
                            </tr>
                            <tr>
                                <td>
                                    Subjects:
                                    <%#DataBinder.Eval(Container.DataItem, "Subjects")%>            
                                    <%--Created Date: <%#DataBinder.Eval(Container.DataItem, "CreatedDate")%>--%>
                                </td>
                            </tr>
                             <tr>
                                <td>
                                    Locations:
                                    <%#DataBinder.Eval(Container.DataItem, "Location")%> 
                                   
                                </td>
                            </tr>
                            <tr>
                                <td>
                                    Description:
                                    <%#DataBinder.Eval(Container.DataItem, "Description")%>
                                </td>
                            </tr>
                           
                                                   
                        </table><br /><br />
                    </ItemTemplate>
                    <FooterTemplate>
                    </FooterTemplate>
                </asp:DataList>
                
                <table width="100%" border="0">
        <tr bgcolor=""  align="center">

            <td>
                <asp:LinkButton ID="lnkbtnPrevious" runat="server" Text="<" OnClick="lnkbtnPrevious_Click"></asp:LinkButton>
            </td>
            <td>
                <asp:DataList ID="dlPaging" runat="server" RepeatDirection="Horizontal" OnItemDataBound="dlPaging_ItemDataBound"
                    OnItemCommand="dlPaging_ItemCommand" OnSelectedIndexChanged="dlPaging_SelectedIndexChanged"
                    UseAccessibleHeader="True">
                    <ItemTemplate>
                        <asp:LinkButton ID="lnkbtnPaging" runat="server" CommandArgument='<%#Eval("PageIndex")%>'
                            CommandName="lnkbtnPaging" Text='<%#Eval("PageText")%>'></asp:LinkButton>  
                    </ItemTemplate>
                </asp:DataList>
            </td>
            <td>
                <asp:LinkButton ID="lnkbtnNext" runat="server" Text=">" OnClick="lnkbtnNext_Click"></asp:LinkButton>
            </td>
        </tr>
    </table>
            </td>
            
        </tr>
    </table>

using System;
using System.Data;
using System.Web.UI.WebControls;

public partial class MathsTutors : System.Web.UI.Page
{
    PagedDataSource pds = new PagedDataSource();
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            BindData();
        }
    }
    private void BindData()
    {
        ClsTutorDetails tutor = new ClsTutorDetails();
        DataTable dt = tutor.GetAllTutors("Active");



        pds.DataSource = dt.DefaultView;
        pds.AllowPaging = true;
        pds.PageSize = 12;
        pds.CurrentPageIndex = CurrentPage;
        lnkbtnNext.Enabled = !pds.IsLastPage;
        lnkbtnPrevious.Enabled = !pds.IsFirstPage;

        gv1.DataSource = pds;
        gv1.DataBind();

        if (dt.Rows.Count <= 12)
        {
            dlPaging.Visible = false;
            lnkbtnNext.Visible = false;
            lnkbtnPrevious.Visible = false;
        }
        else
        {
            dlPaging.Visible = true;
            lnkbtnNext.Visible = true;
            lnkbtnPrevious.Visible = true;
        }

        doPaging();



    }

    

    #region

    private void doPaging()
    {
        DataTable dt = new DataTable();
        dt.Columns.Add("PageIndex");
        dt.Columns.Add("PageText");
        for (int i = 0; i < pds.PageCount; i++)
        {
            DataRow dr = dt.NewRow();
            dr[0] = i;
            dr[1] = i + 1;
            dt.Rows.Add(dr);
        }

        dlPaging.DataSource = dt;
        dlPaging.DataBind();
    }

    public int CurrentPage
    {

        get
        {
            if (this.ViewState["CurrentPage"] == null)
                return 0;
            else
                return Convert.ToInt16(this.ViewState["CurrentPage"].ToString());
        }

        set
        {
            this.ViewState["CurrentPage"] = value;
        }

    }
    protected void lnkbtnPrevious_Click(object sender, EventArgs e)
    {
        CurrentPage -= 1;
        BindData();
    }

    protected void lnkbtnNext_Click(object sender, EventArgs e)
    {
        CurrentPage += 1;
        BindData();
    }


    protected void dlPaging_SelectedIndexChanged(object sender, EventArgs e)
    {
        CurrentPage = 0;
        BindData();

    }

    protected void dlPaging_ItemCommand(object source, DataListCommandEventArgs e)
    {
        if (e.CommandName.Equals("lnkbtnPaging"))
        {
            CurrentPage = Convert.ToInt16(e.CommandArgument.ToString());
            BindData();
        }
    }

    protected void dlPaging_ItemDataBound(object sender, DataListItemEventArgs e)
    {
        LinkButton lnkbtnPage = (LinkButton)e.Item.FindControl("lnkbtnPaging");
        if (lnkbtnPage.CommandArgument.ToString() == CurrentPage.ToString())
        {
            lnkbtnPage.Enabled = false;
            lnkbtnPage.Font.Bold = true;

        }
    }
    #endregion
}

@if (User.Identity.IsAuthenticated)
{
	<form asp-controller="Account" asp-action="Logout" method="post" id="logoutForm">
		<ul>
			<li>
				<button type="submit">Log out</button>
			</li>
		</ul>
	</form>
}
else
{
	<ul>
		<li><a asp-page="/Login">Log in</a></li>
	</ul>
}

public async Task<IActionResult> OnPostAsync(string returnUrl = null)
{
    CSDUtil.PWDUtil oUtil = new CSDUtil.PWDUtil();
    try
    {
        ReturnUrl = returnUrl;
        // Verification.
        if (ModelState.IsValid)
        {
            UserDetailsDB data = UserDetails;
            UserDetailsDB oUser = await dsUserDetails.AutenticateAsync(data);
            if (oUser == null)
            {
                ModelState.AddModelError(string.Empty, "Invalid user details.");
                return Page();
            }
            JwtSecurityTokenHandler oHandler = new JwtSecurityTokenHandler();
            var key = Code.MainUI.Key;
            var handler = new JwtSecurityTokenHandler();
            var jwtToken = new JwtSecurityToken(oUser.Token);
            var validations = new TokenValidationParameters
            {
                ValidateIssuerSigningKey = true,
                IssuerSigningKey = new SymmetricSecurityKey(key),
                ValidateIssuer = false,
                ValidateAudience = false
            };
            ClaimsPrincipal oPrincipal = handler.ValidateToken(oUser.Token, validations, out SecurityToken oToken);
            int i = oPrincipal.Claims.Count();
            var authProperties = new AuthenticationProperties
            {
                AllowRefresh = true,
                ExpiresUtc = DateTimeOffset.UtcNow.AddMinutes(60),
                IsPersistent = true,
                IssuedUtc = DateTimeOffset.Now,
                RedirectUri = "/Index"
            };
            await HttpContext.SignInAsync(
                                CookieAuthenticationDefaults.AuthenticationScheme,
                                new ClaimsPrincipal(oPrincipal),
                                authProperties);
            var B = User.Identity.IsAuthenticated;///////this is always false
            return LocalRedirect(Url.GetLocalUrl(returnUrl));
        }
    }

ClaimsPrincipal oPrincipal = handler.ValidateToken(oUser.Token, validations, out SecurityToken oToken);

					returnUrl = "/Index";
					ClaimsIdentity identity = User.Identity as ClaimsIdentity;
					foreach (Claim oClaim in oPrincipal.Claims)
					{
						identity.AddClaim(oClaim);
					}					
					var B = User.Identity.IsAuthenticated;//this is always false
					return LocalRedirect(Url.GetLocalUrl(returnUrl));