How do I check for null or empty string for many arguments? - C#

Question

I have the below method, which I need to check for whether the arguments are empty or null.

    public DB Where(string field, string operat, string value, string andOr, string field2, string operat2, string value2)
    {
        _Where = " WHERE " + field + " " + operat + " @" + field + "1 " + andOr + " " + field2 + " " + operat2 + " @" + field2 + "2 ";
        _Params.Add(field + "1", value);
        _Params.Add(field2 + "2", value2);
        return this;
    }

I have found the string.IsNullOrWhiteSpace method however this would require this much code:

                   if (string.IsNullOrWhiteSpace(field))
            throw new ArgumentException("field Cannot be null or be empty");

        if (string.IsNullOrWhiteSpace(operat))
            throw new ArgumentException("operat Cannot be null or be empty");

        if (string.IsNullOrWhiteSpace(value))
            throw new ArgumentException("value Cannot be null or be empty");

        if (string.IsNullOrWhiteSpace(andOr))
            throw new ArgumentException("andOr Cannot be null or be empty");

        if (string.IsNullOrWhiteSpace(field2))
            throw new ArgumentException("field2 Cannot be null or be empty");

        if (string.IsNullOrWhiteSpace(operat2))
            throw new ArgumentException("operat2 Cannot be null or be empty");

        if (string.IsNullOrWhiteSpace(value2))
            throw new ArgumentException("value2 Cannot be null or be empty");

Is there any way of shortening this?

Also, I have tried creating a custom method for this task, however it throws an exception in the custom method instead of the Where() method which makes it tricky to debug.

Answer 1

You could check the value one by one or creating intermediate function to do that.

Alternatively, my suggestion is: you could put all the inputs in an array and use LINQ Any to check all of them at once:

public DB Where(string field, string operat, string value, string andOr, string field2, string operat2, string value2)
{
    string[] inputs = {field, operat, value, andOr, field2, operat2, value2}
    if (inputs.Any(x => string.IsNullOrWhiteSpace(x))){
        //throw exception
    }
    //continue with your method, all inputs are OK
}

Answer 2

What I can suggest is this:

private string _nullChecker(string _value){
   if (string.IsNullOrWhiteSpace(_value))
            throw new ArgumentException(_value + "Cannot be null or be   empty");
   return _value;
}

then, in your Where string statement

_Where = " WHERE " + _nullChecker(field) + " " + __nullChecker(operat) + " @" + _nullChecker(field) + "1 " + _nullChecker(andOr) + " " + _nullChecker(field2) + " " + _nullChecker(operat2) + " @" + _nullChecker(field2) + "2 ";

Not sure with this though. Haven't checked it with actual code. :) Hope this helps

Answer 3

You could do this:

int? GetLength(string s) {
    return s == "" ? -1 : s?.Length;
}

// s1, s2 and so on are your parameters
int? lengthSum = GetLength(s1) + GetLength(s2); // and so on
int wholeLength = (s1 + s2).Length; // and so on
if(lengthSum == wholeLength) {
    // No parameter is null or empty
}

Answer 4

Firstly, you can use simple libraries to do argument validation. Check out this one called Argument Validator , which has handy functions that will reduce your overall code by half.

Here is an example on how you could do it using the argument validator library:

public DB Where(string field, string operat, string value, string andOr, string field2, string operat2, string value2)
{
    var inputs = new string[] {field, operat, value, andOr, field2, operat2, value2};
    foreach(var input in inputs)
    {
        Throw.IfNullOrEmpty(input, nameof(input)));
    }
}