Building a C# equivalent of the MS SQL construct IN?

Often in MS SQL, I use IN, to check if a value is in a list of items, e.g.

WHERE @x IN (1,2,3,5,8,13)

I’ve got as close as I can by defining the following in a library function, thus:

public static bool IIN(object oValue, params object[] oValues)
{
    int i;

    for (i = 0; i <= oValues.GetUpperBound(0); i++)
    {
        if ((oValue.ToString()) == (oValues[i].ToString())) return true;
    }
    return false;
}

In this way I can call it thus:

bool bItemFound = IIN(x,1,2,3,5,8,13);

However, because it is in a library, I end up having to reference the library, thus:

bool bItemFound = MyProject.Common.Helpers.CoreHelper.IIN(x,1,2,3,5,8,13);

This really clutters the code. I’ve tried declaring a Lambda function thus at the top of my calling class:

Func<object, params object[], bool> IIN = (a, b) => { return MyProject.Common.Helpers.CoreHelper.IIN(a, b); };

But Lambda declarations seem to not like having param arrays. I can make the b parameter an object array, thus:

public static bool IIN2(object oValue, object[] oValues)
{
    int i;

    for (i = 0; i <= oValues.GetUpperBound(0); i++)
        if ((oValue.ToString()) == (oValues[i].ToString())) return true;

    return false;
}

And my Lambda declaration is:

Func <object, object[], bool> IIN = (a, b) => { return CoreHelper.IIN2(a, b); };

But then I have to declare an inline throwaway object[] in my calling code:

bool bItemFound = IIN(x, new object[] { 1,2,3,5,8,13 });

Is there a neater way of doing this, being as clean and as readable as the SQL equivalent?

>Solution :

This really clutters the code.

If the only goal is to remove this part:

MyProject.Common.Helpers.CoreHelper.

Then a using static directive can do that. For example, if you include this directive at the top of the file:

using static MyProject.Common.Helpers.CoreHelper;

Then you can call the method directly:

bool bItemFound = IIN(x,1,2,3,5,8,13);

I haven’t tested this, but you may even be able to combine it with the global using directive in C# 10:

global using static MyProject.Common.Helpers.CoreHelper;

Which should allow the use of that method throughout the files included in the project.