C# DataRow Empty-check

问题:

I got this:

 DataTable dtEntity = CreateDataTable();
 drEntity = dtEntity.NewRow();

Then I add data to the row (or not). Lots of code, really don't know if there's anything inside the row. Depends on the input (i am importing from some files). I'd like to do something like:

 if (drEntity`s EVERY CELL IS NOT EMPTY)
 {
   dtEntity.Rows.Add(drEntity);
 }
 else
 {
   //don't add, will create a new one (drEntity = dtEntity.NewRow();)
 }

Is there some nice way to check if the DataRow's every cell is empty? Or I should foreach, and check them one by one?

回答1:

A simple method along the lines of:

bool AreAllColumnsEmpty(DataRow dr)
{
 if (dr == null)
 {
  return true;
 }
 else
 {
  foreach(var value in dr.ItemArray)
  {
    if (value != null)
    {
      return false;
    }
  }
  return true;
 }
}

Should give you what you're after, and to make it "nice" (as there's nothing as far as I'm aware, in the Framework), you could wrap it up as an extension method, and then your resultant code would be:

if (datarow.AreAllColumnsEmpty())
{
}
else
{
}

回答2:

I created a helper (in a static class I called DataRowHelpers, inventive, I know) called IsEmpty as follows:

public static bool IsEmpty(this DataRow row)
{
    return row == null || row.ItemArray.All(i => i is DBNull);
}

The other answers here are correct. I just felt mine lent brevity in its succinct use of Linq to Objects. BTW, this is really useful in conjunction with Excel parsing since users may tack on a row down the page (thousands of lines) with no regard to how that affects parsing the data.

In the same class, I put any other helpers I found useful, like parsers so that if the field contains text that you know should be a number, you can parse it fluently. Minor pro tip for anyone new to the idea. (Anyone at SO, really? Nah!)

With that in mind, here is an enhanced version:

public static bool IsEmpty(this DataRow row)
{
    return row == null || row.ItemArray.All(i => i.IsNullEquivalent());
}

public static bool IsNullEquivalent(this object value)
{
    return value == null
           || value is DBNull
           || string.IsNullOrWhiteSpace(value.ToString());
}

Now you have another useful helper, IsNullEquivalent which can be used in this context and any other, too. You could extend this to include things like "n/a" or "TBD" if you know that your data has placeholders like that.

回答3:

I prefer approach of Tommy Carlier, but with a little change.

foreach (DataColumn column in row.Table.Columns)
    if (!row.IsNull(column))
      return false;

  return true;

I suppose this approach looks more simple and bright.

回答4:

public static bool AreAllCellsEmpty(DataRow row)
{
  if (row == null) throw new ArgumentNullException("row");

  for (int i = row.Table.Columns.Count - 1; i >= 0; i--)
    if (!row.IsNull(i))
      return false;

  return true;
}

回答5:

I know this has been answered already and it's an old question, but here's an extension method to do the same:

public static class DataExtensions
{
    public static bool AreAllCellsEmpty(this DataRow row)
    {
        var itemArray = row.ItemArray;
        if(itemArray==null)
            return true;
        return itemArray.All(x => string.IsNullOrWhiteSpace(x.ToString()));            
    }
}

And you use it like so:

if (dr.AreAllCellsEmpty())
// etc

回答6:

You could use this:

if(drEntity.ItemArray.Where(c => IsNotEmpty(c)).ToArray().Length == 0)
{
    // Row is empty
}

IsNotEmpty(cell) would be your own implementation, checking whether the data is null or empty, based on what type of data is in the cell. If it's a simple string, it could end up looking something like this:

if(drEntity.ItemArray.Where(c => c != null && !c.Equals("")).ToArray().Length == 0)
{
    // Row is empty
}
else
{
    // Row is not empty
}

Still, it essentially checks each cell for emptiness, and lets you know whether all cells in the row are empty.

回答7:

DataTable.NewRow will initialize each field to:

• the default value for each DataColumn (DataColumn.DefaultValue)

• except for auto-increment columns (DataColumn.AutoIncrement == true), which will be initialized to the next auto-increment value.

• and expression columns (DataColumn.Expression.Length > 0) are also a special case; the default value will depend on the default values of columns on which the expression is calculated.

So you should probably be checking something like:

bool isDirty = false;
for (int i=0; i<table.Columns.Count; i++)
{
    if (table.Columns[i].Expression.Length > 0) continue;
    if (table.Columns[i].AutoIncrement) continue;
    if (row[i] != table.Columns[i].DefaultValue) isDirty = true;
}

I'll leave the LINQ version as an exercise :)

回答8:

AFAIK, there is no method that does this in the framework. Even if there was support for something like this in the framework, it would essentially be doing the same thing. And that would be looking at each cell in the DataRow to see if it is empty.

回答9:

I did it like this:

var listOfRows = new List<DataRow>();
foreach (var row in resultTable.Rows.Cast<DataRow>())
{
    var isEmpty = row.ItemArray.All(x => x == null || (x!= null && string.IsNullOrWhiteSpace(x.ToString())));
    if (!isEmpty)
    {
        listOfRows.Add(row);
    }
}

回答10:

Maybe a better solution would be to add an extra column that is automatically set to 1 on each row. As soon as there is an element that is not null change it to a 0.

then

If(drEntitity.rows[i].coulmn[8] = 1)
{
   dtEntity.Rows.Add(drEntity);
}
 else
 {
   //don't add, will create a new one (drEntity = dtEntity.NewRow();)
 }