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

问题

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.

回答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
}

回答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

回答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
}

回答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)));
    }
}

来源：https://stackoverflow.com/questions/35816997/how-do-i-check-for-null-or-empty-string-for-many-arguments-c-sharp

标签

string

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isnullorempty