dataSet.GetXml() doesn't return xml for null or blank columns
Solution 1
The problem is detailed in this Microsoft KB article: http://support.microsoft.com/default.aspx?scid=kb;EN-US;Q317961. See this previous SO question for more detail: DataSet.GetXml not returning null results.
I don't think there is a good solution to your direct question. Given context, there may be another way to approach the problem though.
Solution 2
One solution that worked for me.
First clone the DataTable, make all columns of type string, replace all null values with string.empty
, then call GetXml
on a new DataSet.
DataTable dtCloned = dt.Clone();
foreach (DataColumn dc in dtCloned.Columns)
dc.DataType = typeof(string);
foreach (DataRow row in dt.Rows)
{
dtCloned.ImportRow(row);
}
foreach (DataRow row in dtCloned.Rows)
{
for (int i = 0; i < dtCloned.Columns.Count; i++)
{
dtCloned.Columns[i].ReadOnly = false;
if (string.IsNullOrEmpty(row[i].ToString()))
row[i] = string.Empty;
}
}
DataSet ds = new DataSet();
ds.Tables.Add(dtCloned);
string xml = ds.GetXml();
Solution 3
I have been searching the whole world for a solution of writing null fields to XML using DataSet.WriteXML(). I found that following works in a performance optimized way. I have created a function for your convenience. Change your dataset tables one after the other by calling the following function and replacing the tables.
private DataTable GetNullFilledDataTableForXML(DataTable dtSource)
{
// Create a target table with same structure as source and fields as strings
// We can change the column datatype as long as there is no data loaded
DataTable dtTarget = dtSource.Clone();
foreach (DataColumn col in dtTarget.Columns)
col.DataType = typeof(string);
// Start importing the source into target by ItemArray copying which
// is found to be reasonably fast for nulk operations. VS 2015 is reporting
// 500-525 milliseconds for loading 100,000 records x 10 columns
// after null conversion in every cell which may be usable in many
// circumstances.
// Machine config: i5 2nd Gen, 8 GB RAM, Windows 7 64bit, VS 2015 Update 1
int colCountInTarget = dtTarget.Columns.Count;
foreach (DataRow sourceRow in dtSource.Rows)
{
// Get a new row loaded with data from source row
DataRow targetRow = dtTarget.NewRow();
targetRow.ItemArray = sourceRow.ItemArray;
// Update DBNull.Values to empty string in the new (target) row
// We can safely assign empty string since the target table columns
// are all of string type
for (int ctr = 0; ctr < colCountInTarget; ctr++)
if (targetRow[ctr] == DBNull.Value)
targetRow[ctr] = String.Empty;
// Now add the null filled row to target datatable
dtTarget.Rows.Add(targetRow);
}
// Return the target datatable
return dtTarget;
}
Ben
Updated on June 15, 2022Comments
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Ben almost 2 years
When I call dataSet.GetXml() I don't get any xml returned for columns with null or blank values. Is there a simple, efficient way to get around this? An example of the problem below. Notice how a2 is missing from the second results section.
<results> <a1>test1</a1> <a2>test2</a2> <a3>test3</a3> </results> <results> <a1>Atest1</a1> <a3>Atest3</a3> </results>
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Marc Gravell over 13 yearsWhat value would you put in for a null? Perhaps consider giving the column a default value?
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Ben over 13 yearsI would just have the value as blank. I was hoping that there was a way to get all of the xml schema info without having to explicitly set column default values, or do any sort of looping though the xml as I have to do this for many different result sets.
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John Saunders over 13 yearsblank is not the same thing as null
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John Saunders over 13 yearspossible duplicate of DataSet.GetXml not returning null results
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Matt Taylor about 10 yearsYou definitely need to add some explanation to this answer to tell us why you've added this to an already answered question
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Prateek Gupta almost 7 yearsOne edit: If dtCloned.Rows is zero then we should add -> if (dtCloned.Rows.Count == 0) dtCloned.Rows.Add();