Generate auto incremented id based on last string value using C# in ASP.Net

For this you need to store last generated Id somewhere.(i.e. in Database) like below.

SQL

CREATE TABLE GenerateUniqueId
(
    ID INT IDENTITY,
    UniqueId INT NOT NULL
)

HTML

<asp:Button Text="CId" runat="server" OnClick="NewCId" />
<br />
New CID:&nbsp;<asp:Label ID="lblNewCId" runat="server" ForeColor="Red" />

Code

C#

string connStr = ConfigurationManager.ConnectionStrings["conString"].ConnectionString;
protected void NewCId(object sender, EventArgs e)
{
    string previousCidQuery = "SELECT MAX(UniqueId) UniqueId FROM GenerateUniqueId";
    int newCID = GenerateNewCID(connStr, previousCidQuery);
    lblNewCId.Text = newCID.ToString();
    string insertQuery = "INSERT INTO GenerateUniqueId VALUES(" + newCID + ")";
    InsertNewCID(connStr, insertQuery);
}

private void InsertNewCID(string connection, string query)
{
    using (SqlConnection con = new SqlConnection(connection))
    {
        con.Open();
        SqlCommand cmd = new SqlCommand(query, con);
        cmd.ExecuteNonQuery();
        con.Close();
    }
}

private int GenerateNewCID(string connection, string query)
{
    string newCID = string.Empty;
    using (SqlConnection con = new SqlConnection(connection))
    {
        con.Open();
        SqlCommand cmd = new SqlCommand(query, con);
        SqlDataReader dr = cmd.ExecuteReader();
        while (dr.Read())
        {
            string i = dr[0].ToString();
            if (string.IsNullOrEmpty(i))
            {
                newCID = DateTime.Now.ToString("yyMM") + "0000";
            }
            else
            {
                i = i.Substring(4);
                int j = Convert.ToInt32(i);
                j = j + 1;
                newCID = DateTime.Now.ToString("yyMM") + j.ToString().PadLeft(4, '0');
            }
        }
        con.Close();
    }

    return int.Parse(newCID);
}

VB.Net

    Private connStr As String = ConfigurationManager.ConnectionStrings("conString").ConnectionString

    Protected Sub NewCId(ByVal sender As Object, ByVal e As EventArgs)
        Dim previousCidQuery As String = "SELECT MAX(UniqueId) UniqueId FROM GenerateUniqueId"
        Dim newCID As Integer = GenerateNewCID(connStr, previousCidQuery)
        lblNewCId.Text = newCID.ToString()
        Dim insertQuery As String = "INSERT INTO GenerateUniqueId VALUES(" & newCID & ")"
        InsertNewCID(connStr, insertQuery)
    End Sub

    Private Sub InsertNewCID(ByVal connection As String, ByVal query As String)
        Using con As SqlConnection = New SqlConnection(connection)
            con.Open()
            Dim cmd As SqlCommand = New SqlCommand(query, con)
            cmd.ExecuteNonQuery()
            con.Close()
        End Using
    End Sub

    Private Function GenerateNewCID(ByVal connection As String, ByVal query As String) As Integer
        Dim newCID As String = String.Empty

        Using con As SqlConnection = New SqlConnection(connection)
            con.Open()
            Dim cmd As SqlCommand = New SqlCommand(query, con)
            Dim dr As SqlDataReader = cmd.ExecuteReader()

            While dr.Read()
                Dim i As String = dr(0).ToString()

                If String.IsNullOrEmpty(i) Then
                    newCID = DateTime.Now.ToString("yyMM") & "0000"
                Else
                    i = i.Substring(4)
                    Dim j As Integer = Convert.ToInt32(i)
                    j = j + 1
                    newCID = DateTime.Now.ToString("yyMM") & j.ToString().PadLeft(4, "0"c)
                End If
            End While

            con.Close()
        End Using

        Return Integer.Parse(newCID)
    End Function

Screenshot