Hi kankon,

You need to loop through the GridView rows instead of ViewState data.

HTML

<%@ Register Assembly="Microsoft.ReportViewer.WebForms, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"
    Namespace="Microsoft.Reporting.WebForms" TagPrefix="rsweb" %>
 
<form id="form1" runat="server">
<asp:GridView ID="Gridview1" CssClass="grid" runat="server" ShowFooter="true" AutoGenerateColumns="false">
    <Columns>
        <asp:BoundField DataField="RowNumber" HeaderText="Row Number" />
        <asp:TemplateField HeaderText="Header 1">
            <ItemTemplate>
                <asp:DropDownList ID="ddl1" runat="server">
                    <asp:ListItem Text="--Selected--" Value="--Selected--" Selected="True"></asp:ListItem>
                    <asp:ListItem Text="Mango" Value="1"></asp:ListItem>
                    <asp:ListItem Text="Graphs" Value="2"></asp:ListItem>
                    <asp:ListItem Text="Apple" Value=" 3"></asp:ListItem>
                    <asp:ListItem Text="Papaya" Value="4"></asp:ListItem>
                </asp:DropDownList>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Header 2">
            <ItemTemplate>
                <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Header 3">
            <ItemTemplate>
                <asp:TextBox ID="TextBox3" runat="server"></asp:TextBox>
            </ItemTemplate>
            <FooterStyle HorizontalAlign="Right" />
            <FooterTemplate>
                <asp:Button ID="ButtonAdd" runat="server" Text="Add New Row" OnClick="ButtonAdd_Click" />
            </FooterTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<hr />
<asp:Button ID="btnReport" runat="server" Text="Report" OnClick="OnReport" />
<hr />
<rsweb:ReportViewer ID="ReportViewer1" runat="server" Visible="false">
</rsweb:ReportViewer>
</form>

Namespaces

C#

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

Code

C#

private void SetInitialRow()
{
    DataTable dt = new DataTable();
    DataRow dr = null;
    dt.Columns.Add(new DataColumn("RowNumber", typeof(string)));
    dt.Columns.Add(new DataColumn("Column1", typeof(string)));
    dt.Columns.Add(new DataColumn("Column2", typeof(string)));
    dt.Columns.Add(new DataColumn("Column3", typeof(string)));
    dr = dt.NewRow();
    dr["RowNumber"] = 1;
    dr["Column1"] = string.Empty;
    dr["Column2"] = string.Empty;
    dr["Column3"] = string.Empty;
    dt.Rows.Add(dr);

    //Store the DataTable in ViewState
    ViewState["CurrentTable"] = dt;

    Gridview1.DataSource = dt;
    Gridview1.DataBind();
}

private void AddNewRowToGrid()
{
    int rowIndex = 0;

    if (ViewState["CurrentTable"] != null)
    {
        DataTable dtCurrentTable = (DataTable)ViewState["CurrentTable"];
        DataRow drCurrentRow = null;
        if (dtCurrentTable.Rows.Count < 5)
        {
            for (int i = 1; i <= dtCurrentTable.Rows.Count; i++)
            {
                DropDownList ddl1 = (DropDownList)Gridview1.Rows[rowIndex].FindControl("ddl1");
                TextBox box2 = (TextBox)Gridview1.Rows[rowIndex].Cells[2].FindControl("TextBox2");
                TextBox box3 = (TextBox)Gridview1.Rows[rowIndex].Cells[3].FindControl("TextBox3");

                drCurrentRow = dtCurrentTable.NewRow();
                drCurrentRow["RowNumber"] = i + 1;
                if (ddl1.SelectedIndex > 0)
                {
                    dtCurrentTable.Rows[i - 1]["Column1"] = ddl1.SelectedItem.Text;
                }
                dtCurrentTable.Rows[i - 1]["Column2"] = box2.Text;
                dtCurrentTable.Rows[i - 1]["Column3"] = box3.Text;

                rowIndex++;
            }
            dtCurrentTable.Rows.Add(drCurrentRow);
            ViewState["CurrentTable"] = dtCurrentTable;

            Gridview1.DataSource = dtCurrentTable;
            Gridview1.DataBind();
        }
        else
        {
            ClientScript.RegisterClientScriptBlock(this.GetType(), "alert", "alert('Maximum 5 Rows Allow');", true);
        }
    }
    else
    {
        Response.Write("ViewState is null");
    }

    //Set Previous Data on Postbacks
    SetPreviousData();
}


private void SetPreviousData()
{
    int rowIndex = 0;
    if (ViewState["CurrentTable"] != null)
    {
        DataTable dt = (DataTable)ViewState["CurrentTable"];
        if (dt.Rows.Count > 0)
        {
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                DropDownList ddl1 = (DropDownList)Gridview1.Rows[rowIndex].FindControl("ddl1");
                TextBox box2 = (TextBox)Gridview1.Rows[rowIndex].Cells[2].FindControl("TextBox2");
                TextBox box3 = (TextBox)Gridview1.Rows[rowIndex].Cells[3].FindControl("TextBox3");
                ddl1.ClearSelection();
                if (ddl1.Items.FindByText(dt.Rows[i]["Column1"].ToString()) != null)
                {
                    ddl1.Items.FindByText(dt.Rows[i]["Column1"].ToString()).Selected = true;
                }
                box2.Text = dt.Rows[i]["Column2"].ToString();
                box3.Text = dt.Rows[i]["Column3"].ToString();

                rowIndex++;
            }

        }
        Gridview1.DataSource = (DataTable)ViewState["CurrentTable"];
    }
}

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

protected void ButtonAdd_Click(object sender, EventArgs e)
{
    AddNewRowToGrid();
}

protected void OnReport(object sender, EventArgs e)
{
    DataSet1 dsCustomers = new DataSet1();
    foreach (GridViewRow row in Gridview1.Rows)
    {
        DropDownList ddl1 = (DropDownList)row.FindControl("ddl1");
        TextBox box2 = (TextBox)row.FindControl("TextBox2");
        TextBox box3 = (TextBox)row.FindControl("TextBox3");
        string fruits = ddl1.SelectedItem.Text;
        string name = box2.Text;
        string city = box3.Text;
        dsCustomers.Tables[0].Rows.Add(fruits, name, city);
    }
    ReportViewer1.ProcessingMode = ProcessingMode.Local;
    ReportViewer1.LocalReport.ReportPath = Server.MapPath("~/Report.rdlc");
    ReportDataSource datasource = new ReportDataSource("DataSet1", dsCustomers.Tables[0]);
    ReportViewer1.LocalReport.DataSources.Clear();
    ReportViewer1.LocalReport.DataSources.Add(datasource);
    ReportViewer1.Visible = true;
}

Screenshot