How can I make one query out of many others

[User 11883281]

I know.. the "else if" have to be an "if" please ignor it Thank you thats much shorter... but maybe its going shorter?

[Pete OHanlon]

Why not use the Dynamic LINQ Library to do this? Here's some useful info: ScottGu[^].

[User 11883281]

Thank you, but I do not have experience in dynamic Linq, and i don't have time to study it now, isn't there any other way?

[Pete OHanlon]

No, there isn't and Dynamic LINQ isn't hard - you could have learned it in the time you waited for my reply. Honestly, it looks like you didn't even read the link I put in the previous post - if you had, you'd have seen that you can mix and match your standard "from x in ...." syntax with Dynamic LINQ, so you only need to touch the one place.

[Richard Deeming]

Not sure it's technically shorter, but you could build a dictionary to map your selection variable to a filter, and store that map as a private field in your class:

private static readonly Dictionary<string, Expression<Func<object_1, bool>>> Filters = new Dictionary<string, Expression<Func<object_1, bool>>>
{
{ "bild", item => item.bild == null },
{ "machine_group", item => item.machine_group == null },
};

You would then use that dictionary to look up the filter:

var query = from item in _db.object_1
where item.article_number != null
&& item.brand.StartsWith(marke)
&& (item.o_path.StartsWith(pathwerkzeug) || item.o_path.StartsWith(pathgarten));

Expression<Func<object_1, bool>> filter;
if (Filters.TryGetValue(selection, out filter))
{
query = query.Where(filter);
}

erg = query.Select(item => item.article_number);

---

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

[User 11883281]

Thank you that looks good, i will try it.

[User 11883281]

Okay now I get a few errors... 1.:

A query body must end with a select clause or a group clause

2.:

'System.Collections.Generic.IEnumerable' does not contain a definition for 'Where' and the best extension method overload 'System.Linq.Queryable.Where(System.Linq.IQueryable, System.Linq.Expressions.Expression>)' has some invalid arguments

3.:

The type of the expression in the select clause is incorrect. Type inference failed in the call to 'Select'.

4.:

The type arguments for method 'System.Linq.Enumerable.Select(System.Collections.Generic.IEnumerable, System.Func)' cannot be inferred from the usage. Try specifying the type arguments explicitly.

5.:

Instance argument: cannot convert from 'System.Collections.Generic.IEnumerable' to 'System.Linq.IQueryable'

[Richard Deeming]

I suspect they're all related. Try adding a select clause to the end of the first query:

var query = from item in _db.object_1
where item.article_number != null
&& item.brand.StartsWith(marke)
&& (item.o_path.StartsWith(pathwerkzeug) || item.o_path.StartsWith(pathgarten))
select item;

---

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

[User 11883281]

Thanks ;) it WAS working ... and then I changed it for all and now theres this errro:

System.TypeInitializationException: Der Typeninitialisierer für "Quälix.AbfrageIsNull" hat eine Ausnahme verursacht. ---> System.ArgumentException: Ein Element mit dem gleichen Schlüssel wurde bereits hinzugefügt.
bei System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)
bei System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
bei System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value)
bei Quälix.AbfrageIsNull..cctor() in q:\PIM_PolicingTool\Quälix\Quälix\AbfrageIsNull.cs:Zeile 12.
--- Ende der internen Ausnahmestapelüberwachung ---
bei Quälix.AbfrageIsNull.ArtikelAufNullPruefen(String selection, List`1 marken)
bei Quälix.Form1.btAbfragIsNullSuche_Click(Object sender, EventArgs e) in q:\PIM_PolicingTool\Quälix\Quälix\Form1.cs:Zeile 56.

this is my code:

if (chbAbfrageArtikel.Checked == true)
{
endErgebnis += "ARTIKEL:";
endErgebnis += Environment.NewLine;
string zwischenErg = AbfrageIsNull.ArtikelAufNullPruefen(selection, marken);

                if (zwischenErg == "") { endErgebnis += "Alles zugeordnet"; }
                else { endErgebnis += zwischenErg; }

                endErgebnis += Environment.NewLine;
                endErgebnis += Environment.NewLine;
            }
            if (chbAbfrageZubehoer.Checked == true)
            {
                endErgebnis += "ZUBEHÖR:";
                endErgebnis += Environment.NewLine;
                string zwischenErg =  "";// AbfrageIsNull.ZubehoerAufNullPruefen(selection, marken);

                if (zwischenErg == "") { endErgebnis += "Alles zugeordnet"; }
                else { endErgebnis += zwischenErg; }

                endErgebnis += Environment.NewLine;
                endErgebnis += Environment.NewLine;
            }
            if (chbAbfrageErsatzteil.Checked == true)
            {
                endErgebnis += "ERSATZTEILE:";
                endErgebnis += Environment.NewLine;
                string zwischenErg = "";// AbfrageIsNull.ErsatzteilAufNullPruefen(selection, marken);                    
                if (zwischenErg == "") { endErgebnis += "Alles zugeordnet"; }
                else { endErgebnis += zwischenErg; }

[Richard Deeming]

The error message is quite clear - "An item with the same key has already been added". In your dictionary initializer, you have added the key "Inventurart" twice - the 6th and 29th items. Remove one of those items.

---

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer