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String.Format not taking 4th object

Here is my prob, I wanted String.Format() function should take 4 objects and format string. But it throws "Input string not in a correct format error".
Here is my code,
string jsonData = string.Format("{{\"sectionTitle\":\"{0}\",\"strPushMsg\":\"{1}\",\"Language\":\"{2}\",}\",\"articleid\":\"{3}\"}}", urlsectiontitle, formatHeadline, Language, articleid);

\"{2}\",}\"
Looks like you need to escape that closing brace by doubling it:
string.Format("{{\"sectionTitle\":\"{0}\",\"strPushMsg\":\"{1}\",\"Language\":\"{2}\",}}\",\"articleid\":\"{3}\"}}", urlsectiontitle, formatHeadline, Language, articleid);
It appears you are creating JSON. This can use single quotes (which would avoid all the escaping), but even better use a tool like JSON.Net designed to create JSON. While your (partial) structure here is quite small (the unmatched } shows this is only partial), and the JSON gets bigger it is much easier to use a tool to get it right.

Automatically escaping characters within strings

I am working on a C# project where I am exporting data from a database that is defined by the user so I have no idea what the data is going to contain or the format it is going to be in.
Some of the strings within the database might include apostrophe's (') which I need to escape but everything I've found on the internet shows that I would have to do string.replace("'", "\'"); which seems a bit odd as it would be a mass of replace statements for every possibility.
Isn't there a better way to do this.
Thanks for any help you can provide.

I recently had to make a code fix for this same problem. I had to put a ton of string.replace() statements everywhere. My recommendation would be to create a method that handles all escape character possibilities and have your query strings pass through this method before being executed. If you design your structure correctly you should only have to call this method once.
public string FixEscapeCharacterSequence(string query)
{
query = query.Replace("'", "\'");
//..Any other replace statements you need
//....
return query;
}

custom string format puzzler

We have a requirement to display bank routing/account data that is masked with asterisks, except for the last 4 numbers. It seemed simple enough until I found this in unit testing:
string.Format("{0:****1234}",61101234)
is properly displayed as: "****1234"
but
string.Format("{0:****0052}",16000052)
is incorrectly displayed (due to the zeros??): "****1600005252""
If you use the following in C# it works correctly, but I am unable to use this because DevExpress automatically wraps it with "{0: ... }" when you set the displayformat without the curly brackets:
string.Format("****0052",16000052)
Can anyone think of a way to get this format to work properly inside curly brackets (with the full 8 digit number passed in)?
UPDATE: The string.format above is only a way of testing the problem I am trying to solve. It is not the finished code. I have to pass to DevExpress a string format inside braces in order for the routing number to be formatted correctly.

It's a shame that you haven't included the code which is building the format string. It's very odd to have the format string depend on the data in the way that it looks like you have.
I would not try to do this in a format string; instead, I'd write a method to convert the credit card number into an "obscured" string form, quite possibly just using Substring and string concatenation. For example:
public static string ObscureFirstFourCharacters(string input)
{
// TODO: Argument validation
return "****" + input.Substring(4);
}
(It's not clear what the data type of your credit card number is. If it's a numeric type and you need to convert it to a string first, you need to be careful to end up with a fixed-size string, left-padded with zeroes.)

I think you are looking for something like this:
string.Format("{0:****0000}", 16000052);
But I have not seen that with the * inline like that. Without knowing better I probably would have done:
string.Format("{0}{1}", "****", str.Substring(str.Length-4, 4);
Or even dropping the format call if I knew the length.
These approaches are worthwhile to look through: Mask out part first 12 characters of string with *?
As you are alluding to in the comments, this should also work:
string.Format("{0:****####}", 16000052);
The difference is using the 0's will display a zero if no digit is present, # will not. Should be moot in your situation.
If for some reason you want to print the literal zeros, use this:
string.Format("{0:****\0\052}", 16000052);
But note that this is not doing anything with your input at all.

Replacing backslash in a string

I am having a few problems with trying to replace backslashes in a date string on C# .net.
So far I am using:
string.Replace(#"\","-")
but it hasnt done the replacement. Could anyone please help?

string.Replace does not modify the string itself but returns a new string, which most likely you are throwing away. Do this instead:
myString= myString.Replace(#"\","-");
On a side note, this kind of operation is usually seen in code that manually mucks around with formatted date strings. Most of the time there is a better way to do what you want (which is?) than things like this.

as all of them saying you need to take value back in the variable.
so it should be
val1= val1.Replace(#"\","-");
Or
val1= val1.Replace("\\","-");
but not only .. below one will not work
val1.Replace(#"\","-");

Use it this way.
oldstring = oldstring.Replace(#"\","-");
Look for String.Replace return type.
Its a function which returns a corrected string. If it would have simply changed old string then it would had a void return type.

You could also use:
myString = myString.Replace('\\', '-'));
but just letting you know, date slashes are usually forward ones /, and not backslashes \.

As suggested by others that String.Replace doesn't update the original string object but it returns a new string instead.
myString= myString.Replace(#"\","-");
It's worthwhile for you to understand that string is immutable in C# basically to make it thread-safe. More details about strings and why they are immutable please see links here and here

state at compile time not known

I need a way to Parse an string into an integer value in c#. The problem is the user chosses a string from a combo box which contains strings such as "AAAAA" or "5". That means only at run time it is known if the parameter is a real string or an string which can be parsed to an integer. I tried around with reflection and have the fitting Parameter object.
ParameterInfo p = ps[i];
Type t = p.ParameterType;
I don't know how to go on from there or if it even is possible. I can't use if else statments because the program is supposed to load other interfaces with new parameters as well. So I could handle the default ones with if else statmentes but when a new interface with new Methodinfos is loaded that dos not work anymore.

I'm not usre that understood all your constraints. However you can parse string by using Int32.TryParse in case target string is not necessarily valid.

Int32.TryParse whould help you with that

To parse a string into an integer, you can use Convert.ToInt32(string_var), or any of the other conversion methods. See here for more.