to check whether given value present in sqldatabase?

SqlCommand cmd = new SqlCommand("Your Command using where clause","your Connection");
            SqlDataReader dr = cmd.ExecuteReader();
            if (dr.Read()) // if reading 
            {
// values is present 
            }
           else { // not present}

// Create database connection
SqlConnection con = new SqlConnection(<Connection string goes where>);
con.Open(); // Open

// Check for value
SqlCommand cmd = new SqlCommand("SELECT id FROM tbl WHERE name='Kim'", con);

// Get value
object value = cmd.ExecuteScalar();

// Close database connection
con.Close();

// Check for value
if (value == null)
  Console.WriteLine("Value not in table");
else
  Console.WriteLine("Value found at id: " + value);

Dim con As New SqlConnection("Your Connection String")
       If con.State = ConnectionState.Closed Then
           con.Open()
       End If
       Dim cmd As SqlCommand = New SqlCommand("Select * from YourTableName Where YourColumnName='" & YourValue & "'")
       Dim rd As SqlDataReader = cmd.ExecuteReader()
       If rd.Read = True Then
           'code here when value exist
           Response.Write("Your value exists in table")
       Else
           Response.Write("Your value does not exist..")
       End If