Handle Null value of DropDownList selection using FindByText in ASP.Net

Hi akhter,

Refer below sample.

HTML

<asp:GridView runat="server" AutoGenerateColumns="false" ID="gvCustomers" OnSelectedIndexChanged="gvCustomers_SelectedIndexChanged">
    <Columns>
        <asp:BoundField DataField="CustomerId" HeaderText="Id" />
        <asp:BoundField DataField="Name" HeaderText="Name" />
        <asp:BoundField DataField="Country" HeaderText="Country" />
        <asp:CommandField ShowSelectButton="true" />
    </Columns>
</asp:GridView>
<br />
<asp:DropDownList runat="server" ID="ddlName">
</asp:DropDownList>
<br />
<asp:DropDownList runat="server" ID="ddlCountry">
</asp:DropDownList>

Namespaces

C#

using System.Data;
using System.Data.SqlClient;
using System.Configuration;

VB.Net

Imports System.Data
Imports System.Data.SqlClient
Imports System.Configuration

Code

C#

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!this.IsPostBack)
        {
            DataTable dt = GetData();
            gvCustomers.DataSource = dt;
            gvCustomers.DataBind();

            ddlCountry.DataSource = dt;
            ddlCountry.DataValueField = "Country";
            ddlCountry.DataTextField = "Country";
            ddlCountry.DataBind();
            ddlCountry.Items.Insert(0, new ListItem(" ", "0"));

            ddlName.DataSource = dt;
            ddlName.DataValueField = "Name";
            ddlName.DataTextField = "Name";
            ddlName.DataBind();
            ddlName.Items.Insert(0, new ListItem(" ", "0"));
        }
    }

    private static DataTable GetData()
    {
        string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
        using (SqlConnection con = new SqlConnection(constr))
        {
            using (SqlCommand cmd = new SqlCommand("SELECT CustomerId, Name, Country FROM CustomerTest", con))
            {
                using (SqlDataAdapter da = new SqlDataAdapter(cmd))
                {
                    DataTable dt = new DataTable();
                    da.Fill(dt);
                    return dt;
                }
            }
        }
    }

    protected void gvCustomers_SelectedIndexChanged(object sender, EventArgs e)
    {
        int index = gvCustomers.SelectedIndex;
        string name = gvCustomers.SelectedRow.Cells[1].Text;
        string country = gvCustomers.SelectedRow.Cells[2].Text;

        if (ddlName.Items.FindByText(name) != null)
        {
            ddlName.ClearSelection();
            ddlName.Items.FindByText(name).Selected = true;
            if (ddlCountry.Items.FindByText(country) != null)
            {
                ddlCountry.ClearSelection();
                ddlCountry.Items.FindByText(country).Selected = true;
            }
            else
            {
                ddlCountry.SelectedIndex = 0;
            }
        }
        if (ddlCountry.Items.FindByText(country) != null)
        {
            ddlCountry.ClearSelection();
            ddlCountry.Items.FindByText(country).Selected = true;
            if (ddlName.Items.FindByText(name) != null)
            {
                ddlName.ClearSelection();
                ddlName.Items.FindByText(name).Selected = true;
            }
            else
            {
                ddlName.SelectedIndex = 0;
            }
        }
    }

VB.Net

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)Handle Me.Load
        If Not Me.IsPostBack Then
            Dim dt As DataTable = GetData()
            gvCustomers.DataSource = dt
            gvCustomers.DataBind()
            ddlCountry.DataSource = dt
            ddlCountry.DataValueField = "Country"
            ddlCountry.DataTextField = "Country"
            ddlCountry.DataBind()
            ddlCountry.Items.Insert(0, New ListItem(" ", "0"))
            ddlName.DataSource = dt
            ddlName.DataValueField = "Name"
            ddlName.DataTextField = "Name"
            ddlName.DataBind()
            ddlName.Items.Insert(0, New ListItem(" ", "0"))
        End If
    End Sub

    Private Shared Function GetData() As DataTable
        Dim constr As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString

        Using con As SqlConnection = New SqlConnection(constr)

            Using cmd As SqlCommand = New SqlCommand("SELECT CustomerId, Name, Country FROM CustomerTest", con)

                Using da As SqlDataAdapter = New SqlDataAdapter(cmd)
                    Dim dt As DataTable = New DataTable()
                    da.Fill(dt)
                    Return dt
                End Using
            End Using
        End Using
    End Function

    Protected Sub gvCustomers_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs)
        Dim index As Integer = gvCustomers.SelectedIndex
        Dim name As String = gvCustomers.SelectedRow.Cells(1).Text
        Dim country As String = gvCustomers.SelectedRow.Cells(2).Text

        If ddlName.Items.FindByText(name) IsNot Nothing Then
            ddlName.ClearSelection()
            ddlName.Items.FindByText(name).Selected = True

            If ddlCountry.Items.FindByText(country) IsNot Nothing Then
                ddlCountry.ClearSelection()
                ddlCountry.Items.FindByText(country).Selected = True
            Else
                ddlCountry.SelectedIndex = 0
            End If
        End If

        If ddlCountry.Items.FindByText(country) IsNot Nothing Then
            ddlCountry.ClearSelection()
            ddlCountry.Items.FindByText(country).Selected = True

            If ddlName.Items.FindByText(name) IsNot Nothing Then
                ddlName.ClearSelection()
                ddlName.Items.FindByText(name).Selected = True
            Else
                ddlName.SelectedIndex = 0
            End If
        End If
    End Sub

Screenshot