Develop Reference

Can't Figure Out Missing Parameter Error When Running an Oracle Query

I am very new to database queries and even more so, Oracle. I am also new to development work and, believe it or not, am creating this an for work purely out of frustration with the current process. Anyway, I am attempting to collect input from a multi-line text box and run a query. Each line corresponds to a single string that needs to be passed into the WHERE statement and the results will be dumped into a data table. Unfortunately, Oracle has still not released its developer tools for VS2019 so I am having to do this the harder way.
UPDATE # 2:
I have completely rebuilt the query since it was not running even when using known working code from another query. Below is what I have pieced together from various places on the interwebs. While debugging, it appears to parse and format the text correctly and pass it into the OracleParameter without issue. I am getting a Missing Expression error but I don't know what I am missing.
var connString =
ConfigurationManager.ConnectionStrings["dB"].ConnectionString;
string query = "SELECT col1, col2, col3, col4 FROM table WHERE col5 IN (";
using (OracleConnection conn = new OracleConnection(connString))
try
{
var input = "";
input = uniLookup.UniList;
var uniList = string.Join(",", Regex.Split(input, #"(?:\r\n|\n|\r)"));
string allParams = uniList;
string formattedParams = allParams.Replace(" ", string.Empty);
string[] splitParams = formattedParams.Split(',');
List<OracleParameter> parameters = new List<OracleParameter>();
using (OracleCommand cmd = new OracleCommand(query, conn))
{
for (int i = 0; i < splitParams.Length; i++)
{
query += #":Uni" + i + ",";
parameters.Add(new OracleParameter(":Uni" + i, splitParams[i]));
{
query = query.Substring(0, (query.Length - 1));
query += ')';
conn.Open();
using (OracleDataReader reader = cmd.ExecuteReader()) <==ERROR
{
if (!reader.HasRows)
{
while (reader.Read())
{
reader.Read();
{
MessageBox.Show(reader.GetString(1));
}
}
}

You can use IN in your where clause in this way to get rows from multiple values as:
string query = "SELECT dummyCol FROM dummytable WHERE altCol IN ("+text+");";
where you just have to change your text as text="'value1','value2','value3'"; this will not produce any syntax error.
You can convert your multi line text into same comma separated values using this :
foreach (String s in textBox1.Text.Split('\n'))
{
text +="'"+ s+"',";
}
text = text.TrimEnd(',');
this will help you achieve what you need. you can ask If there is any confusion.
Your final code will become :
public void GetData()
{
if (string.IsNullOrWhiteSpace(textbox1.Text) || textbox1.Text == "")
{
MessageBox.Show("Please Enter at least 1 Value and Try Again!");
}
else
{
System.Data.DataTable dt = new System.Data.DataTable();
// string[] lines = textbox1.Text.Split('\n');
string text = "";
foreach (String s in textBox1.Text.Split('\n'))
{
text += "'" + s + "',";
}
text = text.TrimEnd(',');
//Connection Credentials
string credentials = "Credentials";
string query = "SELECT dummyCol FROM dummytable WHERE altCol IN ("+text+");";
OracleConnection conn = new OracleConnection(credentials);
try
{
//Open The Connection
conn.Open();
using (OracleCommand cmd = new OracleCommand(query, conn))
{
//Call the Oracle Reader
using (OracleDataReader reader = cmd.ExecuteReader())
{
if (!reader.HasRows)
{
MessageBox.Show("Unable to Retrieve Data");
return;
}
else if (reader.HasRows)
{
reader.Read();
DataRow row = dt.NewRow();
// create variables to accept reader data for each column
// insert data from query into each column here
dt.Rows.Add(row);
}
}
}
}
}
}

SQL Server CE not supporting ExecuteSQLCommand with EF?

I've been developing a C# WPF project with VS2015 using SQL Server Express LocalDb with Entity Framework. I have built a custom seeder for the database, that reads test data from an Excel file, that simply combines the Excel data into a command string, and this is inserted using context.Database.ExecuteSQLCommand.
Now, I was thinking of launching the project with SQL Server Compact Edition 4.0, but I find this command is not working anymore. Do I have to write my uploader again using SqlCeConnection and SqlCeCommand or am I missing something?
Also, from somewhere I have understood that with EF you can switch the SQL provider and the code would not need other changes. Am I in for more surprises down the road?
Example of the uploader command:
string cmd = "INSERT INTO Venues(Name, City, Telephone) Values ('X','Y','Z')"
context.Database.ExecuteSqlCommand(cmd);
The error:
There was an error parsing the query. [ Token line number = 2,Token line offset = 1,Token in error = INSERT ]
This is not just a testing issue, as I would want to include this uploader in the production version, too, for quick inserting of master data (e.g. employee list).
EDIT: Uploader code. If this can be done without resorting to raw SQL, that would be a good solution, too.
This loops through Excel sheets (named after entities) and columns (first row has property name) and rows 2->n (data). This handles the upload of basically any amount of data within Excel limitations. The point is that the code has no knowledge of the entities (might have been possible to parameterize DataContext too). Code might not be optimal, as I'm just a beginner, but has worked for me, except not with SQL CE. Editing to suit CE is not a big issue, but I wanted to ask for possibly better ways.
public static class ExcelUploader
{
static ArrayList data;
static List<string> tableNames;
public static string Upload(string filePath)
{
string result = "";
data = new ArrayList();
tableNames = new List<string>();
ArrayList upLoadData = ReadFile(filePath);
List<string> dataList = ArrayListToStringList(upLoadData);
using (var db = new DataContext())
{
using (var trans = db.Database.BeginTransaction())
{
try
{
foreach (var cmd in dataList)
{
Console.WriteLine(cmd);
db.Database.ExecuteSqlCommand(cmd);
}
db.SaveChanges();
trans.Commit();
}
catch (Exception e)
{
trans.Rollback();
result = e.Message;
MessageBox.Show(result);
}
}
}
return result;
}
private static ArrayList ReadFile(string fileName)
{
List<string> commands = new List<string>();
var xlApp = new Microsoft.Office.Interop.Excel.Application();
var wb = xlApp.Workbooks.Open(fileName, ReadOnly: true);
xlApp.Visible = false;
foreach (Worksheet ws in wb.Worksheets)
{
var r = ws.UsedRange;
var array = r.Value;
data.Add(array);
tableNames.Add(ws.Name);
}
wb.Close(SaveChanges: false);
xlApp.Quit();
return data;
}
private static List<string> ArrayListToStringList(ArrayList arrList)
{
List<string> result = new List<string>();
for(int tableAmount = 0;tableAmount<data.Count;tableAmount++)
{
result.Add(ArrayToSqlCommand(arrList[tableAmount] as Array, tableNames[tableAmount]));
}
return result;
}
private static string ArrayToSqlCommand(Array arr, string tableName)
{
int propertyRow = 1;
int firstDataRow = 2;
string command = "";
// loop rows
for (int rowIndex = firstDataRow; rowIndex <= arr.GetUpperBound(0); rowIndex++)
{
command += "INSERT INTO " + tableName + "(";
//add column names
for (int colIndex = 1; colIndex <= arr.GetUpperBound(1); colIndex++)
{
//get property name
command += arr.GetValue(propertyRow, colIndex);
//add comma if not last column, otherwise close bracket
if (colIndex == arr.GetUpperBound(1))
{
command += ") Values (";
}
else
{
command += ", ";
}
}
//add values
for (int colIndex = 1; colIndex <= arr.GetUpperBound(1); colIndex++)
{
//get property value
command += "'" + arr.GetValue(rowIndex, colIndex) + "'";
//add comma if not last column, otherwise close bracket
if (colIndex == arr.GetUpperBound(1))
{
command += ");";
}
else
{
command += ", ";
}
}
command += "\n";
}
return command;
}
}

There are two ways to use raw SQL queries I'd offer.
Initial data
1) Excel table
+=======+=======+===========+
| Name | City | Telephone |
|===========================|
| Adam | Addr1 | 111-11-11 |
|-------|-------|-----------|
| Peter | Addr2 | 222-22-22 |
+-------+-------+-----------+
2) SQL Server CE table
CREATE TABLE Venues
(
Id int identity primary key,
[Name] nvarchar(100) null,
City nvarchar(100) null,
Telephone nvarchar(100) null
);
3) Getting data from Excel
Here we're interested in getting array from Excel sheet. As soon as we get it, we can safely close Excel. The code assumes file "Employees.xlsx" to be next to executable file.
private object[,] GetExcelData()
{
xlApp = new Excel.Application { Visible = false };
var xlBook =
xlApp.Workbooks.Open(System.IO.Path.Combine(
Environment.CurrentDirectory,
"Employees.xlsx"));
var xlSheet = xlBook.Sheets[1] as Excel.Worksheet;
// For process termination
var xlHwnd = new IntPtr(xlApp.Hwnd);
var xlProc = Process.GetProcesses()
.Where(p => p.MainWindowHandle == xlHwnd)
.First();
// Get Excel data: it's 2-D array with lower bounds as 1.
object[,] arr = xlSheet.Range["A1"].CurrentRegion.Value;
// Shutdown Excel
xlBook.Close();
xlApp.Quit();
xlProc.Kill();
GC.Collect();
GC.WaitForFullGCComplete();
return arr;
}
Now you can use one of the ways to generate query.
Option 1. Use ExecuteSqlCommand
When using ExecuteSqlCommand, it's advisable to use parameterized queries to avoid errors. You can pass explicitly created SqlCeParameter or just pass a value.
private void UseExecuteSqlCommand()
{
object[,] arr = GetExcelData();
using (var db = new EmpContext())
{
db.Database.Initialize(true);
int count = 0;
string sql = "INSERT INTO Venues (Name, City, Telephone) " +
"VALUES (#name, #city, #phone);";
// Start from 2-nd row since we need to skip header
for (int r = 2; r <= arr.GetUpperBound(0); ++r)
{
db.Database.ExecuteSqlCommand(
sql,
new SqlCeParameter("#name", (string)arr[r, 1]),
new SqlCeParameter("#city", (string)arr[r, 2]),
new SqlCeParameter("#phone", (string)arr[r, 3])
);
++count;
}
conn.Close();
MessageBox.Show($"{count} records were saved.");
}
}
Option 2. Use DbConnection
If you want your code to be more generic, you can create method which would accept DbConnection. This will allow to pass either SqlConnection or SqlCeConnection. But the code becomes more verbose because we can't use constructors since these classes are abstract.
private void UseDbConnection()
{
object[,] arr = GetExcelData();
using (var db = new EmpContext())
{
db.Database.Initialize(true);
int count = 0;
string sql = "INSERT INTO Venues (Name, City, Telephone) " +
"VALUES (#name, #city, #phone);";
DbParameter param = null;
DbConnection conn = db.Database.Connection;
conn.Open();
DbCommand command = conn.CreateCommand();
command.CommandText = sql;
command.CommandType = CommandType.Text;
// Create parameters
// Name
param = command.CreateParameter();
param.ParameterName = "#name";
command.Parameters.Add(param);
// City
param = command.CreateParameter();
param.ParameterName = "#city";
command.Parameters.Add(param);
// Telephone
param = command.CreateParameter();
param.ParameterName = "#phone";
command.Parameters.Add(param);
// Start from 2-nd row since we need to skip header
for (int r = 2; r <= arr.GetUpperBound(0); ++r)
{
command.Parameters["#name"].Value = (string)arr[r, 1];
command.Parameters["#city"].Value = (string)arr[r, 2];
command.Parameters["#phone"].Value = (string)arr[r, 3];
command.ExecuteNonQuery();
++count;
}
conn.Close();
MessageBox.Show($"{count} records were saved.");
}
}
You can also use ordinal positions for parameters which eliminates creating parameters names and makes code much shorter:
private void UseDbConnection()
{
object[,] arr = GetExcelData();
using (var db = new EmpContext())
{
db.Database.Initialize(true);
int count = 0;
// Take a note - use '?' as parameters
string sql = "INSERT INTO Venues (Name, City, Telephone) " +
"VALUES (?, ?, ?);";
DbConnection conn = db.Database.Connection;
conn.Open();
DbCommand command = conn.CreateCommand();
command.CommandText = sql;
command.CommandType = CommandType.Text;
// Create parameters
command.Parameters.Add(command.CreateParameter());
command.Parameters.Add(command.CreateParameter());
command.Parameters.Add(command.CreateParameter());
for (int r = 2; r <= arr.GetUpperBound(0); ++r)
{
// Access parameters by position
command.Parameters[0].Value = (string)arr[r, 1];
command.Parameters[1].Value = (string)arr[r, 2];
command.Parameters[2].Value = (string)arr[r, 3];
command.ExecuteNonQuery();
++count;
}
conn.Close();
MessageBox.Show($"{count} records were saved.");
}
}
P.S.
I didn't check whether the underlying connection is opened, but it's a good idea to do so.

Based on JohnyL's excellent input, I was able to modify my code so that it works with either SQL Server Express and and SQL Server CE. I'll put my new code as an answer, as I had to parameterize it further, as I couldn't write the property names in the code either. But this was a simple step, once I got the idea from JohnyL. Not sure though, if the database writing operation should be wrapped inside a DbTransaction, but this worked for now.
public static class ExcelUploader
{
static ArrayList data;
static List<string> tableNames;
static List<DbCommand> cmdList = new List<DbCommand>();
static DbConnection conn;
public static void Upload(string filePath)
{
data = new ArrayList();
tableNames = new List<string>();
//get Excel data to array list
ArrayList upLoadData = ReadFile(filePath);
using (var db = new DataContext())
{
conn = db.Database.Connection;
//transform arraylist into a list of DbCommands
ArrayListToCommandList(upLoadData);
conn.Open();
try
{
foreach (var cmd in cmdList)
{
//Console.WriteLine(cmd.CommandText);
cmd.ExecuteNonQuery();
}
}
catch (Exception e)
{
var result = e.Message;
MessageBox.Show(result);
}
}
}
//opens Excel file and reads worksheets to arraylist
private static ArrayList ReadFile(string fileName)
{
List<string> commands = new List<string>();
var xlApp = new Microsoft.Office.Interop.Excel.Application();
var wb = xlApp.Workbooks.Open(fileName, ReadOnly: true);
xlApp.Visible = false;
foreach (Worksheet ws in wb.Worksheets)
{
var r = ws.UsedRange;
var array = r.Value;
data.Add(array);
tableNames.Add(ws.Name);
}
wb.Close(SaveChanges: false);
xlApp.Quit();
return data;
}
//transforms arraylist to a list of DbCommands
private static void ArrayListToCommandList(ArrayList arrList)
{
List<DbCommand> result = new List<DbCommand>();
for (int tableAmount = 0; tableAmount < data.Count; tableAmount++)
{
ArrayToSqlCommands(arrList[tableAmount] as Array, tableNames[tableAmount]);
}
}
private static void ArrayToSqlCommands(Array arr, string tableName)
{
//Excel row which holds property names
int propertyRow = 1;
//First Excel row with values
int firstDataRow = 2;
string sql = "";
DbCommand cmd = conn.CreateCommand();
sql += "INSERT INTO " + tableName + "(";
//add column names to command text
for (int colIndex = 1; colIndex <= arr.GetUpperBound(1); colIndex++)
{
//get property name
sql += arr.GetValue(propertyRow, colIndex);
//add comma if not last column, otherwise close bracket
if (colIndex == arr.GetUpperBound(1))
{
sql += ") Values (";
}
else
{
sql += ", ";
}
}
//add value parameter names to command text
for (int colIndex = 1; colIndex <= arr.GetUpperBound(1); colIndex++)
{
//get property name
sql += "#" + arr.GetValue(propertyRow, colIndex);
//add comma if not last column, otherwise close bracket
if (colIndex == arr.GetUpperBound(1))
{
sql += ");";
}
else
{
sql += ", ";
}
}
//add data elements as command parameter values
for (int rowIndex = firstDataRow; rowIndex <= arr.GetUpperBound(0); rowIndex++)
{
//initialize command
cmd = conn.CreateCommand();
cmd.CommandText = sql;
cmd.CommandType = CommandType.Text;
for (int colIndex = 1; colIndex <= arr.GetUpperBound(1); colIndex++)
{
//set parameter values
DbParameter param = null;
param = cmd.CreateParameter();
param.ParameterName = "#" + (string)arr.GetValue(propertyRow, colIndex);
cmd.Parameters.Add(param);
cmd.Parameters[param.ParameterName].Value = arr.GetValue(rowIndex, colIndex);
}
//add command to command list
cmdList.Add(cmd);
}
}
}

Get Names ForEach Checked item in Checkedlistbox

I want to get the names associated with the states i select in my program. Below is the code that i currently have. My database has multiple locations within a state that have different contacts. I just want to select a state and acquire everyone under that state. Thanks for the help!
con = new OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=F:\\Database\\LocNo.accdb");
con.Open();
foreach (Object c in checkedListBox2.CheckedItems)
{
if (checkedListBox2.GetItemCheckState(checkedListBox2.Items.IndexOf(c)) == CheckState.Checked)
{
str1 += c.ToString() + ",";
flag = 1;
}
}
i = 0;
allSelectedtypestring = "";
allSelected = str1.Split(',');
while (allSelected.Length - 1 > i)
{
str = "select c1 from table where state ='" + allSelected[i++] + "'";
cmd = new OleDbCommand(str, con);
dr = cmd.ExecuteReader();
dr.Read();
allSelectedtypestring += dr.GetString(11);
}
label30.Text = Convert.ToString(allSelectedtypestring);
con.Close();

You can use the following code to retrieve the contacts:
var states = new List<string>();
foreach (Object c in checkedListBox2.CheckedItems)
{
states.Add(c.ToString());
flag = 1; // Can also be substituted by states.Count > 0
}
using(var con = new OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=F:\\Database\\LocNo.accdb"))
{
con.Open();
using(var cmd = con.CreateCommand())
{
var paramIndex = 0;
var paramClause = new System.Text.StringBuilder(100);
foreach(var state in states)
{
if (paramClause.Length > 0)
paramClause.Append(", ");
paramClause.Append("?");
var paramName = "State" + (paramIndex++).ToString();
cmd.Parameters.AddWithValue(paramName, state);
}
var paramsClause = string.Join(", ", cmd.Parameters.
cmd.CommandText = "select distinct c1 from table where state IN (" + paramsClause.ToString() + ")";
using(var rdr = cmd.ExecuteReader())
{
var contacts = new List<string>();
while(rdr.Read())
{
contacts.Add(rdr.GetString(0);
}
label30.Text = string.Join(", ", contacts);
}
}
}
Please note that I've made the following changes:
Added using statements to reliably dispose the connection, command and reader.
Used a List<string> as a more convenient way to collect the selected states.
Added DISTINCT to the SELECT in order to filter duplicate entries.
Used a parameter in the command text in order to avoid SQL injection attacks. Though this way to use a parameter with an IN clause works for SQL Server, I haven't checked whether it also works for an Access database. Let me know in the comments if it doesn't work.

How to retrieve all fields for a given record using OracleDataReader?

My question, which is similar to this one, is how can I use OracleDataReader to retrieve all the fields for a given record? Currently, I've been using this method, which returns only one column value at a time:
public string Select_File(string filename, string subdirectory, string envID)
{
Data_Access da = new Data_Access();
OracleConnection conn = da.openDB();
OracleCommand cmd = new OracleCommand();
cmd.Connection = conn;
cmd.CommandText = "SELECT * FROM EIP_Deployment_Files"
+ " WHERE Filename ='" + filename + "'"
+ " AND Subdirectory = '" + subdirectory + "'"
+ " AND Environment_ID = '" + envID + "'";
cmd.CommandType = CommandType.Text;
string x;
OracleDataReader dr = cmd.ExecuteReader();
if (dr.HasRows) // file exists in DB
{
dr.Read();
x = dr.GetString(2).ToString(); // return baseline filename (index 2)
}
else
{
x = "New File";
}
cmd.Dispose();
da.CloseDB(conn);
return x;
}
I'm sure that this method is far from perfect and ppl will be quick to point that out (I was basically given it by my supervisor since I didn't have any prior experience in ASP.NET) but all I really care about is that it works. My question is: how can it be modified to return all the fields for a given record?
The fields will be of either VARCHAR2, CHAR, or DATE datatypes, (if that makes a difference) and some of these values may be null. I'm thinking I could convert them to strings and return them as a list?

if u want something like this:
List<User> lstUser = new List<User>();
string sqlQuery = "Select * from User_T where User_Name='" + oUser.UserName + "' And Password='" +oUser.Password + "' AND IsActive='"+1+"' AND IsDelete='"+0+"'";
string connectionString = "Data Source=ORCL;User Id=ACCOUNTS;Password=ACCOUNTS";
using (DBManager dbManager = new DBManager(connectionString))
{
try
{
dbManager.Open();
OracleDataReader dataReader = dbManager.ExecuteDataReader(sqlQuery);
while (dataReader.Read())
{
oUser = new User();
oUser.Id = Convert.ToInt32(dataReader["ID"]);
oUser.CompanyId = Convert.ToInt32(dataReader["Company_ID"]);
oUser.BranchId = Convert.ToInt32(dataReader["Branch_ID"]);
oUser.UserName = Convert.ToString(dataReader["User_Name"]);
lstUser.Add(oUser);
}
dataReader.Close();
dataReader.Dispose();
}
catch
(Exception)
{
}
finally
{
dbManager.Close();
dbManager.Dispose();
}

To read all the data from the columns of the current row in a DataReader, you can simply use GetValues(), and extract the values from the array - they will be Objects, of database types.
Object[] values;
int numColumns = dr.GetValues(values); //after "reading" a row
for (int i = 0; i < numColumns; i++) {
//read values[i]
}
MSDN - "For most applications, the GetValues method provides an efficient means for retrieving all columns, rather than retrieving each column individually."

Sorry for posting an answer to a very old question. As none of the answers are correct (either they have security issues or not checking for DBNull), I have decided to post my own.
public async Task<StringBuilder> FetchFileDetailsAsync(string filename, string subdirectory, string envId)
{
var sb = new StringBuilder();
//TODO: Check the parameters
const string connectionString = "user id=userid;password=secret;data source=" +
"(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=10.0.0.8)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=xe)))";
const string selectQuery = "SELECT * FROM EIP_Deployment_Files"
+ " WHERE Filename = :filename"
+ " AND Subdirectory = :subdirectory"
+ " AND Environment_ID = :envID"
+ " AND rownum<=1";
using (var connection = new OracleConnection(connectionString))
using (var cmd = new OracleCommand(selectQuery, connection) {BindByName = true, FetchSize = 1 /*As we are expecting only one record*/})
{
cmd.Parameters.Add(":filename", OracleDbType.Varchar2).Value = filename;
cmd.Parameters.Add(":subdirectory", OracleDbType.Varchar2).Value = subdirectory;
cmd.Parameters.Add(":envID", OracleDbType.Varchar2).Value = envId;
//TODO: Add Exception Handling
await connection.OpenAsync();
var dataReader = await cmd.ExecuteReaderAsync(CommandBehavior.CloseConnection);
var rowValues = new object[dataReader.FieldCount];
if (dataReader.Read())
{
dataReader.GetValues(rowValues);
for (var keyValueCounter = 0; keyValueCounter < rowValues.Length; keyValueCounter++)
{
sb.AppendFormat("{0}:{1}", dataReader.GetName(keyValueCounter),
rowValues[keyValueCounter] is DBNull ? string.Empty : rowValues[keyValueCounter])
.AppendLine();
}
}
else
{
//No records found, do something here
}
dataReader.Close();
dataReader.Dispose();
}
return sb;
}

weird result with c# winForms array of Lists

so I'm trying to store values in an array of Lists in C# winForms. In the for loop in which I make the sql statment, everything works fine: the message box outputs a different medication name each time.
for (int i = 0; i < numberOfMeds; i++)
{
queryStr = "select * from biological where medication_name = '" + med_names[i] + "' and patient_id = " + patientID.patient_id;
using (var conn = new SqlConnection(connStr))
using (var cmd = new SqlCommand(queryStr, conn))
{
conn.Open();
using (SqlDataReader rdr = cmd.ExecuteReader())
{
while (rdr.Read())
{
medObject.medication_date = (DateTime)rdr["patient_history_date_bio"];
medObject.medication_name = rdr["medication_name"].ToString();
medObject.medication_dose = Convert.ToInt32(rdr["medication_dose"]);
medsList[i].Add(medObject);
}
}
conn.Close();
MedicationTimelineClass medObjectx = medsList[i][0] as MedicationTimelineClass;
MessageBox.Show(medObjectx.medication_name);
}
}
but then, when I take the message box code out of the loop, meaning that the array of Lists is supposed to be populated, I always get the same value: the last value entered. the same medication name, no matter what number I put between those brackets. It's like if the whole array of Lists is populated with the same data.
for (int i = 0; i < numberOfMeds; i++)
{
queryStr = "select * from biological where medication_name = '" + med_names[i] + "' and patient_id = " + patientID.patient_id;
using (var conn = new SqlConnection(connStr))
using (var cmd = new SqlCommand(queryStr, conn))
{
conn.Open();
using (SqlDataReader rdr = cmd.ExecuteReader())
{
while (rdr.Read())
{
medObject.medication_date = (DateTime)rdr["patient_history_date_bio"];
medObject.medication_name = rdr["medication_name"].ToString();
medObject.medication_dose = Convert.ToInt32(rdr["medication_dose"]);
medsList[i].Add(medObject);
}
}
conn.Close();
}
}
MedicationTimelineClass medObjectx = medsList[0][0] as MedicationTimelineClass;
MessageBox.Show(medObjectx.medication_name);
what's going on here?

It looks like you are reusing the same MedicationTimelineClass object inside your loop. Remember that your class is a reference type. You are basically adding the same reference to your list and updating the values of the properties stored in the object at that reference. Ultimately, all of the "items" in your list refer to the same object.
Instantiate a new MedicationTimelineClass object with each iteration and then add that new object to your list.

In the "while (rdr.Read())" loop, you're just adding the same object (medObject) to the list each time. The list is being populated with the same object, over and over again.