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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.

How to remove the double quotes variable in c#

My project has different SQL Server DataTable. I will bind the data from user request table. so got table name as
Example:
table = "MyTable"
How to write the SQL query for select the particular table.
con.open();
SqlAdaptor da = new SqlAdaptor ("select * from '" + table.replace(""", "\"")" + '")
cmd.ExecuteNonQuery();
My replace is not working so I hope to any one resolve my issue.

Just escape " character?1
table.Replace("\"", string.Empty);
Also you don't need single quotes for your table name. By the way if you get this table as an input, I will strongly suggest do some strong validation before you put it in your query or use a whitelist.
You didn't show us rest of your code but use using statement to dispose your connection and adapter objects.
1: Since it is an escape sequence character

You can also try
SqlAdaptor da = new SqlAdaptor ("Select * from " + table.Replace('"', ' ').Trim());

string table = "MyTable";
table.Replace('\"', ' '); //Or
table.Replace('\"',string.Empty);

Oracle data access error: ORA-00936: missing expression

I am accessing an Oracle database in my asp.net application, and am getting this error:
ORA-00936: missing expression
My c# code is:
getInfoByPoNum =
"SELECT h.SYS_HEADER_ID,
h.FOLIO1 AS INV_NUMBER,
v.VENDOR_NAME,
CASE WHEN h.Comments LIKE '%CLOSED%' THEN 'CLOSED' ELSE NVL(h.Comments, 'OPEN') END AS CComments,
h.ORG_ID
FROM INV_HEADERS h, VENDORS v
WHERE h.LOOKUP_CODE in ('STANDARD', 'BLANKET')
AND h.VENDOR_ID = v.VENDOR_ID
AND h.FOLIO1 = #invNumber"
OracleCommand CMD = new OracleCommand();
OracleConnection CONN = new OracleConnection(constring.ConnectionString);
CMD.Connection = CONN;
CONN.Open();
CMD.Parameters.Clear();
CMD.Parameters.Add(new OracleParameter("#invNumber", INVNumber));
CMD.CommandText = getInfoByPoNum;
using (var reader = CMD.ExecuteReader())
{
while (reader.Read())
{
The error occurs at CMD.ExecuteReader().
Based on other posts on SO and on the web, the query is correct and runs in oracle sql-developer.
What is causing the syntax error?
Update: If I modify the oracle query and enter a valid invoice number value instead of #invNumber, the query executes fine in my application.
getInfoByPoNum =
"SELECT h.SYS_HEADER_ID,
h.FOLIO1 AS INV_NUMBER,
v.VENDOR_NAME,
CASE WHEN h.Comments LIKE '%CLOSED%' THEN 'CLOSED' ELSE NVL(h.Comments, 'OPEN') END AS CComments,
h.ORG_ID
FROM INV_HEADERS h, VENDORS v
WHERE h.LOOKUP_CODE in ('STANDARD', 'BLANKET')
AND h.VENDOR_ID = v.VENDOR_ID
AND h.FOLIO1 = 2241QSA"

I believe that for Oracle your parameter should be specified as :invNumber, not #invNumber in your query:
AND h.FOLIO1 = :invNumber"
And when setting your parameter, it should look like this (just remove the #):
CMD.Parameters.Add(new OracleParameter("invNumber", INVNumber));
EDIT
You may also need to enable parameter binding by name (I think it's positional by default):
CMD.BindByName = true;

Try putting all your query in the same line, it seems that only the first line of the string is being executed. Also check if there isn´t any escape character or special character that you have to treat with a "\" character.

And this may also occur, in my experience, when attempting to execute SQL with a terminating semicolon in the Oracle managed driver for .NET/C#.
So in that situation, execute the SQL within a wrapper for consistency and
do not use
SELECT * FROM X;
use
SELECT * FROM X
in other words, strip it off.

Properly check if a record already exists in a database

I have read other questions on this, but it does not help for the most part.
Trying to check if a file has already been uploaded(filename is sent to this table) before creating another record and allowing them to upload the same file again.
I am using this code and it keeps telling me every file is a new file, even when I use the same file for testing. Obviously it should result in "Exists". Connection is already established using "this.Master.Conn" so please no SQLCommand stuff.
I even tried using wildcards in the query.
private string SQLCheck(string FileName)
{
string Check = "Select VideoURL from TrainingVideo2 where VideoURL Like '" + FileName +"' and Status=1;";
Object ob = this.Master.Conn.ExecuteSqlScalarCommand(Check);
string Result;
if (DBNull.Value.Equals(ob))
{
Result = "Exists";
}
else
{
Result = "NewFile";
}
return Result;
}
Also, does anybody have a better(more efficient) way of doing this?
Trying to basically rewrite this in c#.
Private Function CheckName(name As String) As Int32
Dim sql As String = "SELECT ID FROM Company Where Name Like '" & name & "' "
Dim ob As Object = Conn.ExecuteSqlScalarCommand(sql)
If IsDBNull(ob) Then
Return 0
Else
Return CInt(ob)
End If
End Function

There are new and more innovative methods devised to get around the simple "replace all ` and " characters with ..." SQL injection prevention techniques. In your case, if the VideoURL happens to be a varchar (and not nvarchar), then using unicode character U+02BC (URL encoded = %CA%BC) would pass in a quote character as a unicode string, which would bypass your C# checks, but SQL Server will conveniently convert to a quote character in your query. This is just one example of why you should not be doing this :).
In terms of you check, I always prefer using TOP 1 to let SQL Server cut a potential table scan short. So, I would use this query:
Select TOP 1 SomeNonNullIntColumn from TrainingVideo2 where VideoURL Like ... and Status=1;
Execute the query with ExecuteScalar. If the result is null, then the record does not exist.

Never build up an SQL string like that. See SQL injection.
Why are you using like? Do you really have Sql wildcards in that fileName?
Example (sorry for the "SqlCommand stuff", but it's important):
string sql = "select count(*) from TrainingVideo2 where VideoURL = #Name and Status=1"
using (SqlConnection conn = new SqlConnection(connString))
{
SqlCommand cmd = new SqlCommand(sql, conn);
cmd.Parameters.Add("#Name", fileName);
conn.Open();
return (Int32)cmd.ExecuteScalar() > 0;
}

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
}