CODEWITHSUNDEEP
c#linq
Royi Namir
Royi Namir

Reputation: 148524

Use LINQ to check if all values are "0"?

I have a simple datatable : 

DataTable dt = new DataTable("myTable");
dt.Columns.Add("id", typeof (int));
dt.Columns.Add("John_a", typeof (int));
dt.Columns.Add("Paul_a", typeof (int));
dt.Columns.Add("George_b", typeof (int));
dt.Columns.Add("Ringo_b", typeof (int));
dt.Columns.Add("Yoko_a", typeof (int));

it has one row with data :

DataRow r = dt.NewRow();
r["id"] = 1;
r["John_a"] = 0;
r["Paul_a"] = 0;
r["George_b"] =4;
r["Ringo_b"] = 2;
r["Yoko_a"] =10;

dt.Rows.Add(r);

I need to get a bool answer ( true) only if :

All Values on columns whose name ends with "_a" has value 0

So here , I should get False. why ?

Becuase 

John_a has 0
Paul_a has 0

but

"Yoko_a" (which also ends with "_a") doesn't have "0" but another number.

What have i tried : 

var t =
dt.AsEnumerable().Select(row => dt.Columns.Cast<DataColumn>()
                  .Where(c => c.ColumnName.ToLower().EndsWith("_a")
                              && row.Field<int>(c.ColumnName) == 0
                        )
                    ).Any();

but It returns True....

What am I missing?

Upvotes: 4

Views: 4200

Answers (1)

Tim Schmelter
Tim Schmelter

Reputation: 460068

As the name suggests, use Enumerable.All:

bool allZero = dt.Columns.Cast<DataColumn>()
    .Where(c => c.ColumnName.EndsWith("_a", StringComparison.OrdinalIgnoreCase))
    .All(c => dt.AsEnumerable().All(r => r.Field<int>(c) == 0));

Note that this approach also check all rows of the DataTable, i've asumed that this is what you want. Enumerable.All returns false as soon as one comparison returned false.

Edit

I need only the first row to be checked.

Then it's even easier:

bool allZero = dt.Columns.Cast<DataColumn>()
    .Where(c => c.ColumnName.EndsWith("_a", StringComparison.OrdinalIgnoreCase))
    .All(c => dt.Rows[0].Field<int>(c) == 0);

Upvotes: 6

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