Check value exist in Database or not using LINQ query in ASP.Net

Hi nagaraju60,

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

I have the Database Table and sample record like below.

HTML

<asp:DropDownList runat="server" ID="DropDownList1" AutoPostBack="true" OnSelectedIndexChanged="DropdownChanged"
    AppendDataBoundItems="true">
    <asp:ListItem Text="-Select-" Value="0" />
</asp:DropDownList>
<br />
<asp:Label ID="lblName" runat="server" />

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        DataTable dt = new DataTable();
        dt.Columns.AddRange(new DataColumn[2] { new DataColumn("No"), new DataColumn("Name") });
        dt.Rows.Add(25, "John Hammond");
        dt.Rows.Add(1, "Mudassar Khan");
        dt.Rows.Add(28, "Suzanne Mathews");
        dt.Rows.Add(2, "Maria");
        dt.Rows.Add(3, "Ana Trujillo");
        dt.Rows.Add(4, "Antonio Moreno");
        dt.Rows.Add(5, "Thomas Hardy");
        dt.Rows.Add(6, "Christina Berglund");
        dt.Rows.Add(7, "Hanna Moos");
        dt.Rows.Add(32, "Robert Schidner");
        DropDownList1.DataSource = dt;
        DropDownList1.DataTextField = "Name";
        DropDownList1.DataValueField = "No";
        DropDownList1.DataBind();
    }
}

protected void DropdownChanged(object sender, EventArgs e)
{
    int selectedValue = Convert.ToInt32(DropDownList1.SelectedValue);
    lblName.Text = GetExistingName(selectedValue);
}

private string GetExistingName(int value)
{
    CustomersDataContext dc = new CustomersDataContext();
    string existingName = (from customer in dc.Customers
                            where customer.CustomerId == value
                            select customer.Name).FirstOrDefault();
    return string.IsNullOrEmpty(existingName) ? "" : existingName;
}

Screenshot

Dear Team ,

Thanks for reply, by using below query i am getting sufficient result.

string dtStatus;
string Name=TxtEntrNm.Text;
DataContext DC = new DataContext();
var ExistNm = (from table in DC.TstingTbl.AsEnumerable() where table.EntryName == Name  select table.EntryName).FirstOrDefault();
if (ExistNm  == null)
{
    dtStatus = "";
}
else
{
    dtStatus = ExistNm.ToString();
} 

return dtStatus;