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Fastest way to quote one side of an SQL comparison

I am generating SQL code for different types of databases. To do that dynamically, certain parameters of the SQL script are stored in variables.
One such stored parameter is the comparison expression for certain queries.
Lets say I have a Dogs table with a Name, DateOfBirth and Gender columns, then I have comparison expressions in a variable such as:
string myExpression = "Gender=1";
string myExpression2 = "Gender=1 AND Name='Bucky'";
I would build the following SQL string then:
string mySqlString = "SELECT * FROM "dbo"."Dogs" WHERE " + myExpression;
The problem is, that for Oracle syntax, I have to quote the column names (as seen at dbo.Dogs above). So I need to create a string from the stored expression which looks like:
string quotedExpression = "\"Gender\"=1";
Is there a fast way, to do this? I was thinking of splitting the string at the comparison symbol, but then I would cut the symbol itself, and it wouldn't work on complex conditions either. I could iterate through the whole string, but that would include lot of conditions to check (the comparison symbol can be more than one character (<>) or a keyword (ANY,ALL,etc.)), and I rather avoid lots of loops.

IMO the problem here is the attempt to use myExpression / myExpression2 as naked SQL strings. In addition to being a massive SQL-injection hole, it causes problems like you're seeing now. When I need to do this, I treat the filter expression as a DSL, which I then parse into an AST (using something like a modified shunting yard algorithm - although there are other ways to do it). So I end up with
AND
=
Gender
1
=
Name
'Bucky'
Now I can walk that tree (visitor pattern), looking at each. 1 looks like an integer (int.TryParse etc), so we can add a parameter with that value. 'Bucky' looks like a string literal (via the quotes), so we can add a string-based parameter with the value Bucky (no quotes in the actual value). The other two are non-quoted strings, so they are column names. We check them against our model (white-list), and apply any necessary SQL syntax such as escaping - and perhaps aliasing (it might be Name in the DSL, but XX_Name2_ChangeMe in the database). If the column isn't found in the model: reject it. If you can't understand an expression completely: reject it.
Yes, this is more complex, but it will keep you safe and sane.
There may be libraries that can already do the expression parsing (to AST) for you.

Finding a specific single quote and replacing with double quotes in C#

I've a problem where I want to replace some specific single quotes with double quotes inside a SQL string but not all singles quotes in that string.
EXEC procedureName 'param'eter1', 'parameter2'
In above example I just want to replace the singles quotes inside the 'param'eter1' but the singles quotes in start and end of the parameter to remain same.
Using below command replace all singles quotes in the string and it looks like this ''param''eter1'' which is not correct.
sometext.Replace("'", "''")
I want it to look like this:
EXEC procedureName 'param''eter1', 'parameter2'
Also please note that I am already aware that using SqlParameter is a better solution to handle the single quotes in SQL parameters but due to the restrictions in the project environment I am unable to implement that.
Update:
Changing the individual parameters before using them to construct the full statement is not an option for me as I don't have access to that code. My project works like a data layer where it received SQL strings from other applications to process.

This is a very bad idea. The SQL syntax requires you to escape single quotes in literals exactly because it can otherwise not tell whether the single quote is meant to represent a single quote or meant to terminate the string literal.
Consider the following example:
EXEC procedureName 'param ', ' eter1', 'parameter2'
How would you know whether this is meant to have three parameters for the procedure call or only two? And even if you knew that this specific procedure takes two parameters, you couldn't decide whether the middle part belongs to the first or second parameter.
If the system constructs sql statements from user input without dealing with single quotes before the full statement is constructed, this can be used very easily to attack the system via an sql injection.

you can do like this
var aStringBuilder = new StringBuilder(theString);
aStringBuilder.Remove(3, 2); // just find a position of single quotes
aStringBuilder.Insert(3, "/""); // replace that position with " quotes using loop
theString = aStringBuilder.ToString();

Replacing single quotes in full sql queries with C#

In our C# desktop-application we generate a lot of dynamic sql-queries. Now we have some troubles with single quotes in strings. Here's a sample:
INSERT INTO Addresses (CompanyName) VALUES ('Thomas' Imbiss')
My question is: How can I find and replace all single quotes between 2 other single quotes in a string? Unfortunately I can't replace the single quotes when creating the different queries. I can only do that after the full query is created and right before the query gets executed.
I tried this pattern (Regular Expressions): "\w\'\w"
But this pattern doesn't work, because after "s'" there's a space instead of a char.

I am sorry to say, there is no solution in approach you expect.
For example, have these columns and values:
column A, value ,A',
column B, value ,B',
If they are together in column list, you have ',A',',',B','.
Now, where is the boundary between first and second value? It is ambiguous.
You must take action when creating text fields for SQL. Either use SQL parameters or properly escape qoutes and other problematic characters there.
Consider showing the above ambiguous example to managers, pushing the whole problem back as algorithmically unsolvable at your end. Or offer implementing a guess-work and ask them whether they will be happy if content of several text fields can get mixed in some cases like above one.
At time of SQL query creation, if they do not want to start using SQL parameters, the solution for enquoting any input string is as simple as replacing:
string Enquote(string input)
{
return input.All(c => Strings.AscW(c) < 128) ? "'" : "N'"
+ input.Replace("'", "''")
+ "'"
}
Of course, it can have problem with deliberately malformed Unicode strings (surrogate pairs to hide ') but it is not normally possible to produce these strings through the user interface. Generally this can be still faster than converting all queries to versions with SQL parameters.

Replace all single quotes with two single quotes in a string

I am trying to read value from DB using c#.
The query string contains multiple single quotes - such as: Esca'pes' (the query strings are being read from a text file)
So, I wanted to replace all the single quotes with two single quotes before forming the SQL query. My code is as below:
if (name.Contains('\''))
{
name = name.Replace('\'','\''');
}
How to fix this?

Use strings, not char literals.
name = name.Replace("'", "''");
However it sounds like you're concatenating SQL strings together. This is a huge "DO NOT" rule in modern application design because of the risk of SQL injection. Please use SQL parameters instead. Every modern DBMS platform supports them, including ADO.NET with SQL Server and MySQL, even Access supports them.

name = name.Replace("'","''");
On an unrelated note, you're concatenating strings for use in SQL? Try parameters instead, that's what they're meant for. You're probably making it harder than it needs to be.

Since you want to replace a single character with two characters, you need to use the String overload of Replace
if (name.Contains('\''))
{
name = name.Replace("'","''");
}
(Note: single quotes don't require escaping in Strings like they do in character notation.)

c#: what is the proper way to perform sql LIKE searches using any characters

I'm building (c#) sql select commands strings on the fly using LIKE %somestring% conditions. In my search strings I want to be able to handle any character found on a standard PC (US) keyboard (including ~ ! # # % etc., alt-special chars not required but would be nice to have). I know that single quotes need to be doubled up and perhaps double quotes as well. What other string fixes might be required to ensure correct syntax?

No fixes required:
SqlCommand cmd = new SqlCommand("select * from Foo where Bar like #p", connection);
SqlParameter p = new SqlParameter();
param.ParameterName = "#p";
param.Value = pattern;
cmd.Parameters.Add(param);

Apart from doubling up single quotes (or using a parametrised query), will the user know that "_" and "%" are wildcards (any-character and zero-or-more-any-characters respectively), and that "[...]" creates a closure?
To escape those characters there are two routes
WHERE Foo LIKE '%xxx\%yyy%' ESCAPE '\'
or
WHERE Foo LIKE '%xxx[%]yyy%'
the second uses the side effect of creating a closure, and avoids having to use the ESCAPE (which in itself needs some thought to choose a character that does not conflict with the rest of the string, or is itself escaped where it occurs)
Note that using 'LIKE %somestring%' will usually require a table scan, and may therefore lead to performance problems - e.g. if you have millions of rows to be checked.
In SQL Server you can use sp_ExecuteSQL if you are generating WHERE clauses by string-concatenation - so that only fields that the user specifies criteria for are included. sp_ExecuteSQL will cache the query and, most times, improve performance. (please ask if that it relevant and you need help)