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SQL injection prevention with 'AS QUERY'

I have the following code which seems pretty standard on face value, however in query is another SQL statement hence why the 'AS QUERY' is at the end of the SQL string. I wanted to know if there was a sophisticated approach to parameterising the following SQL command instead of concatenating the entire query together.
The only solution I could think of would be to instead of having a query as a string, have it as an SQLCommand type object and initiate 2 commands. 1 to could and the other to display the preview of the data.
public static CommandStatus<int> GetQueryRecordCount(SqlConnection connection, String query)
{
String sql = "SELECT COUNT(1) FROM (" + query + ") AS QUERY";
SqlCommand cmd = new SqlCommand();
cmd.CommandType = CommandType.Text;
cmd.CommandText = sql;
cmd.Connection = connection;
cmd.CommandTimeout = GetTimeout();
try
{
SqlDataReader dataReader = cmd.ExecuteReader();
dataReader.Read();
String count = dataReader[0].ToString();
dataReader.Close();
return new CommandStatus<int>(Int32.Parse(count));
}
catch (Exception e)
{
return new CommandStatus<int>("Failed to GetQueryRecordCount[" + sql + "]:" + e.Message, e);
}
}
String SQL will end up being something like this
"SELECT COUNT(1) FROM (SELECT TOP 20 [RecordID],[Name],[SonsName],[DadsName],[MothersName],[DaughtersName] FROM [dbo].[sample] ) AS QUERY"

This function is literally SQL injection by design.
Whitelisting the SQL queries this function will accept is the only way to make it safe.
That is, the caller won't be able to inject any SQL query, they'll only be able to pick from a fixed list of pre-vetted queries. The list could even be defined as an array of static strings in the function you show.
But then they don't need to pass the whole query as a string, they only need to pass an ordinal integer to identify which query in the whitelist to run.

Invalid Column Name: "value" - Error Even though it works in another form.

I am stuck at one problem and I just can't solve this.
I get this Error:
Error Message
That's the relevant table
The Code:
SqlConnection connection = new SqlConnection(connectionString);
connection.Open();
string query = "UPDATE CAC SET nextMaintainance = #nextMaintainance WHERE department = " + #departmentCB.Text;
SqlCommand command = new SqlCommand(query, connection);
command.Parameters.AddWithValue("#nextMaintainance", nextMaintainanceDT.Value);
command.ExecuteNonQuery();
The weird thing I don't understand is that a similar code works just fine without any error in my project:
query = "UPDATE LDV SET received = #received, department = #department WHERE Id =" + #idTxt.Text;
command = new SqlCommand(query, connection);
command.Parameters.AddWithValue("#received", inDT.Value);
command.Parameters.AddWithValue("#department", departmentCb.Text);
command.ExecuteNonQuery();
MessageBox.Show("Lungenautomat wurde aktualisiert");
If relevant, my connection string:
connectionString = ConfigurationManager.ConnectionStrings["SCBA_Manager_0._1.Properties.Settings.SCBAmanagerConnectionString"].ConnectionString;
I really hope you can help me :(
Thank you!

The department column is a text column, so comparing it to a value means the value should be wrapped in quotes.
// This fix is not the recommended approach, see the explanation after this code block
string query = "UPDATE CAC SET nextMaintainance = #nextMaintainance WHERE department = '" + departmentCB.Text + "'";
// ^--------------------------^------ single quote added to wrap the value returned by departmentCB.Text
On the other hand, this error does not occur in your second example, because there you're correctly using the Parameters.AddWithValue() method to add the value for the #department parameter, and because id is a numeric column, so it doesn't require the value wrapped in quotes.
However, while the code shown above does the job, it is not the right way of doing the job. The correct way is to used parameters for all values to be injected into a query. The queries you've shown above are already correctly using parameters for some values (e.g. nextMaintenance in the first query, received and department in the second), but are incorrectly doing string concatenation for other values (e.g. department in the first query, id in the second).
Usage of Parameterized SQL
The benefit of using parameterized SQL is that it automatically takes care of adding quotes, prevents SQL injection, etc.
Therefore, its best to change your first code block to:
SqlConnection connection = new SqlConnection(connectionString);
connection.Open();
string query = "UPDATE CAC SET nextMaintainance = #nextMaintainance WHERE department = #department";
SqlCommand command = new SqlCommand(query, connection);
command.Parameters.AddWithValue("#department", departmentCb.Text);
command.Parameters.AddWithValue("#nextMaintainance", nextMaintainanceDT.Value);
command.ExecuteNonQuery();
Notice how the string query is a single string without any messy concatenation, and that it contains two parameters #nextMaintenance and #department? And how the values for those parameters are correctly injected using Parameters.AddWithValue() in the following lines?
Your second code block can be similarly improved by using a parameter for the Id column.
query = "UPDATE LDV SET received = #received, department = #department WHERE Id = #Id ";
command.Parameters.AddWithValue("#Id", idTxt.Text);
Further Information
Do read up about SQL injection ( https://technet.microsoft.com/en-us/library/ms161953(v=sql.105).aspx ) to see how using string concatenation like your original code can lead to various security issues, and why parameterized queries are the preferred way of injecting dynamic values into SQL queries.
You can read up more about parameterized queries here: https://msdn.microsoft.com/en-us/library/yy6y35y8(v=vs.110).aspx

In your first example, the WHERE clause evaluates to
WHERE department = Kasseedorf
wheras it should be
WHERE department = 'Kasseedorf'
So the line should be
string query = "UPDATE CAC SET nextMaintainance = #nextMaintainance WHERE department = '" + #departmentCB.Text +"'";
It works in the second example, because id is an integer and doesn't neet quotes.

SQL Syntax in C#

I'm trying to understand why in C# if you have a sql string why you would have to put tick (') marks in the following where clause in order for this to work. Could someone please explain the reasoning behind this?
where ProgramServer='" + machineName.ToString() + "' and Active=1;

You can avoid those tick (') marks and use Parameters, They will also save you from SQL Injection.
The reason you see those ticks are because SQL expects string type values to be enclosed in single ticks.

What you're seeing is a dynamically built SQL query in the code. When querying based on a string value, the string must be wrapped in single quotes. The final SQL string would look something like:
select * from someTable where ProgramServer = 'YourMachineName' and Active = 1;
Unfortunately, that is far from the best way to do things. You should be using parameterized queries instead:
var query = "select * from someTable where ProgramServer = #machineName and Active = 1;";
using(var conn = new SqlConnection(connString))
{
var command = new SqlCommand(query, conn);
command.Parameters.Add("machineName", machineName.ToString());
// Execute and get the results
}

Is this query to retrieve data from database correct?

I need to retrieve a value from a field in database. I have the used following code. but the value checkOrderId (which I need) shows the SQL string instead of the value from database. I don't know why it is doing so. Could somebody help me please?
string connectionString = "Data Source = xxyyzz;Initial Catalog = xyz; Integrated Security = True";
SqlConnection connection = new SqlConnection(connectionString);
connection.Open();
string tableName = "[GIS].[SecondaryTraffic].[PotentialBackHauls]";
string checkOrderId = "Select TOP 1 OrderID From" + tableName + "ORDER BY InsertDate DESC";
SqlCommand cmd = new SqlCommand(checkOrderId, connection);
//cmd.ExecuteNonQuery();
OpenPop.Pop3.Pop3Client popConn = new OpenPop.Pop3.Pop3Client();
if (orderIdentity == checkOrderId)
{
popConn.DeleteMessage(messageNumber);
}
connection.Close();
I am new and dont have reputation to answer my question immediately. With everybody's help, i got this one solved...Great help, thanx everybody...following is my code.
string connectionString = "Data Source = EAEDEV;Initial Catalog = GIS; Integrated Security = True";
using (SqlConnection connection = new SqlConnection(connectionString))
{
connection.Open();
string tableName = "[GIS].[SecondaryTraffic].[PotentialBackHauls]";
string checkOrderId = "Select TOP 1 OrderID From " + tableName + " ORDER BY InsertDate DESC";
SqlCommand cmd = new SqlCommand(checkOrderId, connection);
string valueReturned = (string)cmd.ExecuteScalar();
OpenPop.Pop3.Pop3Client popConn = new OpenPop.Pop3.Pop3Client();
if (orderIdentity == valueReturned)
{
popConn.DeleteMessage(messageNumber);
}
connection.Close();
}

You need to execute the query and check the results, here you are just comparing a string with the query SQL.
Please see here
http://www.csharp-station.com/Tutorial/AdoDotNet/lesson03
for a tutorial.

Your expectation of the result being set into checkOrderId is incorrect. In this instance checkOrderId is just the query to execute and not the actual result.
You need to read the value back from executing the command:
using (var connection = new SqlConnection(connectionString))
using (var comm = new SqlCommand("Select TOP 1 OrderID From [GIS].[SecondaryTraffic].[PotentialBackHauls] ORDER BY InsertDate DESC", connection))
{
connection.Open();
object result = comm.ExecuteScalar(); // This is the key bit you were missing.
if (result != null)
{
// You can cast result to something useful
int orderId = (int)result;
}
} // Both comm and connection will have Dispose called on them here, no need to Close manually.
ExecuteScalar returns the value in the first cell (ie, column 1 row 1) as an object that you can cast to a better type (depending on what type it was in the result-set schema).
If you need to read multiple values, you need to look at ExecuteReader.
There are also other ways of doing this using output parameters, but that would pollute the point of the answer.

You can add space to your query
"Select TOP 1 OrderID From " + tableName + " ORDER BY InsertDate DESC";
Nota : I suggest you to use AddWithValue method with your parameter
string checkOrderId = "Select TOP 1 OrderID From #tableName ORDER BY InsertDate DESC";
SqlCommand cmd = new SqlCommand(checkOrderId, connection);
cmd.Parameters.AddWithValue("#tableName", tableName );
Link : http://msdn.microsoft.com/fr-fr/library/system.data.sqlclient.sqlparametercollection.addwithvalue.aspx

You don't actually run your command anywhere. Instead of the commented-out cmd.ExecuteNonQuery, you should look into the ExecuteScalar method, which allows you to read back a single result value from a query - which is what your query returns.

Add
int i = (Int32) cmd.ExecuteScalar();
right after
SqlCommand cmd = new SqlCommand(checkOrderId, connection);
then the variable i will contain the order id

No, this is not correct. You are comparing the variable orderId to your query string. I doubt that's what you want to do. I imagine you'd be better off calling cmd.ExecuteScalar() to retrieve the actual OrderID value. As noted by other answers, your query string is missing a space. But most importantly, it is bad practice to construct SQL queries in code. Although I can't see a security issue with this code, if you continue to use this method you will probably write code that is vulnerable to SQL injection. I recommend you learn to either use parameters or LINQ to build your queries.

Error on Quoted Data fetch from Database

i have question that when i fetch data from database and if in the databse have some quoted dat e.g. D`DUN. this data is inserted in DB. when i execute select query like :
Select city from glmast where glname='" + list_customer.Items[i].Value + "'
in list_cutomer there is data in which some data are inserted like D`DUN like quotes. so it gives error like unclosed Quotation.
so, how this will be solved because not all field contain Quotes.
Please Help Me..
Mitesh

You should never use string concatenations when building SQL queries. You should use parametrized queries. Not only that your code will break in situations as the one you have described, but even worse, your code is vulnerable to SQL injection and if your application falls in the hands of malicious users, your database will get busted.
So parametrized queries:
string sql = "SELECT city FROM glmast WHERE glname = #glname";
using (var conn = new SqlConnection("Some connection string"))
using (var cmd = conn.CreateCommand())
{
conn.Open();
cmd.Parameters.AddWithValue("#glname", list_customer.Items[i].Value);
using (var reader = cmd.ExecuteReader())
{
while (reader.Read())
{
// do something with the results
}
}
}