Verifying that a DataTable is sorted

I am working on creating a custom database test condition in Visual Studio, and I am trying to verify a sort order.

I have no problem verifying that the rows in a DataTable are actually sorted, but I also want to verify that each sort column has at least one grouping with more than one distinct value.

I am maintaining a list of integers that define the sorted columns (negative integers indicate a descending sort order - and the absolute value of the integer is the column number).

Let me clarify.

I am writing a unit test condition that verifies a sorted DataTable. I can verify that the row are in the correct sorted order, but I want to verify that the result set contains data that actually tests the sort. In order words, a result set with only one row or any number of duplicate rows is indeed sorted, but that doesn't actually test the sort.

I need to verify that each level of the sort contains at least two distinct values in at leas开发者_StackOverflow中文版t one grouping.

In the past I used a combination of SQL and .Net code and used the following set of queries to make sure there was enough data to test the sort.

SELECT TOP 1 COUNT(DISTINCT column1) 
FROM table 
HAVING COUNT(DISTINCT column1) > 1

SELECT TOP 1 column1, COUNT(DISTINCT column2) 
FROM table 
GROUP BY column1 
HAVING COUNT(DISTINCT column2) > 1

SELECT TOP 1 column1, column2, COUNT(DISTINCT column3)
FROM table
GROUP BY column1, column2
HAVING COUNT(DISTINCT column3) > 1

Where I have a query for each level and all queries must return a non-empty result set in order for the unit test to pass.

My real question is how do I duplicate/convert the SQL code above to LINQ?

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I presume you verify that it's sorted with a double loop along the lines of

for (int i = 1; i < rowCount; i++) {
    for (int j = 0; j < sortColCount; j++) {
        int col = colNum(sortCols[j]);
        int d = Compare(GetValue(rows[i], col), GetValue(rows[i-1], col));
        if (d == 0) continue;
        // Insert here
        Assert(d == colDir(sortCols[j]));
    }
}

What you need to do is where I've put the comment insert a command to flag sort column d as tested (using e.g. a bool array). Then after the loop assert that each sort column is tested.

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You could save the cost of the necessary iteration by hooking the DataTable's TableNewRow, RowChanging and RowChanged events to track/enforce whether or not the DataTable is sequenced the way you expect to be.

Otherwise, it's brute force:

foreach ( int i = 1 ; i < dt.Rows.Length ; ++i )
{
  DataRow prev = dt.Rows[i-1] ;
  DataRow curr = dt.Rows[i  ] ;

  Assert( CompareRows(prev,curr) <= 0 ) ;

}

Where CompareRows(prev,curr) returns the usual sort of comparison result: -1 for prev < curr, 0 for prev == curr and +1 for prev > curr );