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

Refering the below article i have created the example.

Export RDLC Report to PDF without using ReportViewer in ASP.Net with C# and VB.Net

Database

For this example I have used of Northwind database that you can download using the link given below.

Download Northwind Database

HTML

<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<rsweb:ReportViewer ID="ReportViewer1" runat="server" Width="500" SizeToReportContent="true">
</rsweb:ReportViewer>
<br />
<asp:Button ID="btnExport" Text="Open" runat="server" OnClick="Open" />

Namespaces

C#

using System.Data;
using System.Configuration;
using System.Data.SqlClient;
using Microsoft.Reporting.WebForms;

VB.Net

Imports System.Data
Imports System.Configuration
Imports System.Data.SqlClient
Imports Microsoft.Reporting.WebForms

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        ReportViewer1.ProcessingMode = ProcessingMode.Local;
        ReportViewer1.LocalReport.ReportPath = Server.MapPath("~/Report.rdlc");
        Customers dsCustomers = GetData("SELECT TOP 10 * FROM Customers");
        ReportDataSource datasource = new ReportDataSource("Customers", dsCustomers.Tables[0]);
        ReportViewer1.LocalReport.DataSources.Clear();
        ReportViewer1.LocalReport.DataSources.Add(datasource);
    }
}

private Customers GetData(string query)
{
    string conString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    SqlCommand cmd = new SqlCommand(query);
    using (SqlConnection con = new SqlConnection(conString))
    {
        using (SqlDataAdapter sda = new SqlDataAdapter())
        {
            cmd.Connection = con;

            sda.SelectCommand = cmd;
            using (Customers dsCustomers = new Customers())
            {
                sda.Fill(dsCustomers, "DataTable1");
                return dsCustomers;
            }
        }
    }
}

protected void Open(object sender, EventArgs e)
{
    Warning[] warnings;
    string[] streamIds;
    string contentType;
    string encoding;
    string extension;

    //Export the RDLC Report to Byte Array.
    byte[] bytes = ReportViewer1.LocalReport.Render("PDF", null, out contentType, out encoding, out extension, out streamIds, out warnings);

    // Open generated PDF.
    Response.Clear();
    Response.Buffer = true;
    Response.Charset = "";
    Response.Cache.SetCacheability(HttpCacheability.NoCache);
    Response.ContentType = contentType;
    Response.BinaryWrite(bytes);
    Response.Flush();
    Response.End();
}

VB.Net

Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        ReportViewer1.ProcessingMode = ProcessingMode.Local
        ReportViewer1.LocalReport.ReportPath = Server.MapPath("~/Report.rdlc")
        Dim dsCustomers As Customers = GetData("SELECT TOP 10 * FROM Customers")
        Dim datasource As New ReportDataSource("Customers", dsCustomers.Tables(0))
        ReportViewer1.LocalReport.DataSources.Clear()
        ReportViewer1.LocalReport.DataSources.Add(datasource)
    End If
End Sub

Private Function GetData(query As String) As Customers
    Dim conString As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Dim cmd As New SqlCommand(query)
    Using con As New SqlConnection(conString)
        Using sda As New SqlDataAdapter()
            cmd.Connection = con

            sda.SelectCommand = cmd
            Using dsCustomers As New Customers()
                sda.Fill(dsCustomers, "DataTable1")
                Return dsCustomers
            End Using
        End Using
    End Using
End Function

Protected Sub Open(ByVal sender As Object, ByVal e As EventArgs)
    Dim warnings As Warning()
    Dim streamIds As String()
    Dim contentType As String
    Dim encoding As String
    Dim extension As String

    'Export the RDLC Report to Byte Array.
    Dim bytes As Byte() = ReportViewer1.LocalReport.Render("PDF", Nothing, contentType, encoding, extension, streamIds, warnings)

    'Open generated PDF.
    Response.Clear()
    Response.Buffer = True
    Response.Charset = ""
    Response.Cache.SetCacheability(HttpCacheability.NoCache)
    Response.ContentType = contentType
    Response.BinaryWrite(bytes)
    Response.Flush()
    Response.End()
End Sub

Screenshot