convert jsp to c#

[rohitmanhas_12]

hi i want to convert this jsp code to c#...
JSP CODE---------------

ResultSet resultset4;
	try {
    
    Statement statement1 = connection.createStatement();
    String strSQL = ("SELECT * FROM IllnessMaster");
	resultset4 = statement1.executeQuery(strSQL);
	while(resultset4.next())
                         {
                        str2 = resultset4.getString("IllnessId");//Here getting illness ID
						dd = str2.length();//taking IllnessID length
						str5 = str2.substring(1,dd);//here making IllnessId into two parts. because of it contain a charactor followed by number
						int f = Integer.parseInt(str5);
						if (n1<f) //the variable "n1" assign higest number
						n1=f;
						}

--------------------------------------------------------------
I HAD TRIED BUT IT'S GIVING ERROR------

String strSQL = ("SELECT * FROM IllnessMaster");
        SqlCommand cmdSql = new SqlCommand(strSQL, conn);
        conn.Open();

        SqlDataReader r = cmdSql.ExecuteReader();

        String str2 = "";
        int dd = 0;
        String str5 = "";
        int n1 = 0;
        String str3 = "";
        int flag = 0;
        

        while (r.Read())
        {
            str2 = r["IllnessId"].ToString();//Here getting illness ID
            MessageBox.Show("str2=",str2.ToString());
            dd = str2.Length;//taking IllnessID length
           MessageBox.Show("dd=", dd.ToString());
/*LINE-1*/            str5 = str2.Substring(1+dd); //here making IllnessId into two parts. because of it contain a character followed by number
            MessageBox.Show("str5=", str5.ToString());
            int f = Convert.ToInt32(str5);

            if (n1 < f)   //the variable "n1" assign higest number
                n1 = f;
        }

----------ERROR IN LINE-1---------------------------------------------
Exception Details: System.ArgumentOutOfRangeException: startIndex cannot be larger than length of string.
Parameter name: startIndex

[kvprajapati]

Check the length of string before substring

if(str2.Length>(dd+1))
str5 = str2.Substring(1+dd);