I have a DataTable with columns of different types. What I want is a DataTable that has the same column names but all values are strings. That is, if this is the first:
Name Age
-----------
John 31
Alice 27
Marge 45
where Name is a String column and Age is an Int32 column, what I want is:
Name Age
-----------
John 31
Alice 27
Marge 45
where Name and Age are both string columns. The output table must contain the same values as the input table but every value must be converted to a string. Can anyone provide any insight on how one might go about doing this? I thought about maybe doing something like
foreach (DataColumn col in inputTable.Columns)
{
outputTable.Columns.Add(col.ColumnName, typeof(string));
foreach (DataRow row in inputTable.Rows)
{
...??
}
}
Or perhaps there is a better or more efficient approach? Any guidance would be greatly appreciated.
You can't modify a column type in DataTable if already has records. You can Clone DataTable and then modify column type in each column of cloned table. Later you can import rows.
DataTable dtClone = dt.Clone(); //just copy structure, no data
for (int i = 0; i < dtClone.Columns.Count; i++)
{
if (dtClone.Columns[i].DataType != typeof(string))
dtClone.Columns[i].DataType = typeof(string);
}
foreach (DataRow dr in dt.Rows)
{
dtClone.ImportRow(dr);
}
dtClone will have every column as of string and all the data from original table dt
You could use a built in method called toString().
foreach (DataColumn col in inputTable.Columns)
{
outputTable.Columns.Add(col.ColumnName, typeof(string));
foreach (DataRow row in inputTable.Rows)
{
outputTable.Columns.Add(row.toString());
}
}
in this code, you can convert whole dataset in to one string.
string ConvertDatasetToString(DataSet Ds)
{
string OUT = "";
for (int t = 0; t < Ds.Tables.Count; t++)
{
for (int r = 0; r < Ds.Tables[t].Rows.Count; r++)
{
for (int c = 0; c < Ds.Tables[t].Columns.Count; c++)
{
string s = Ds.Tables[t].Rows[r][c].ToString();
OUT += s;
}
}
}
return OUT;
}
if you want to convert one datatable into one string, you can omit the first for
Related
Need an easy method to sum row values(int columns) when a string column value has duplicates in a datatable. And need to remove rows having duplicate values. Below is a datatable for example.
Below table have duplicate "AAA" values, so need to sum Int_Col3,Col4,Col5,Col6,Col7. Note that the columns with Int are integer columns.
Expected Datatable:
Here is a simple method to achieve what you want, in-place. (The same data table is converted to the expected state)
private static void CombineDuplicatesInPlace(DataTable dt)
{
Dictionary<string, DataRow> cachedRows = new Dictionary<string, DataRow>();
for (int i = 0; i < dt.Rows.Count; i++)
{
DataRow dataRow = dt.Rows[i];
string key = Convert.ToString(dataRow["String_Col1"]);
if (cachedRows.ContainsKey(key))
{
DataRow existingRow = cachedRows[key];
foreach (DataColumn dc in dt.Columns)
if (dc.DataType == typeof(int))
existingRow[dc] = (int)existingRow[dc] + (int)dataRow[dc];
dt.Rows.Remove(dataRow);
i--;
}
else { cachedRows[key] = dataRow; }
}
}
I want to be able remove DataRows in a DataTable that contain null values for arrays containing no numeric data.
Trying to modify the code below which transposes the DataTable for use by Google Visualisation API:
private DataTable TransposeOpiate(DataTable inputTable)
{
DataTable outputTable = new DataTable();
// Add columns by looping rows
// Header row's first column is same as in inputTable
outputTable.Columns.Add(inputTable.Columns[0].ColumnName.ToString());
// Header row's second column onwards, 'inputTable's first column taken
foreach (DataRow inRow in inputTable.Rows)
{
string newColName = inRow[0].ToString();
outputTable.Columns.Add(newColName);
}
// Add rows by looping columns
for (int rCount = 1; rCount <= inputTable.Columns.Count - 1; rCount++)
{
DataRow newRow = outputTable.NewRow();
// First column is inputTable's Header row's second column
newRow[0] = inputTable.Columns[rCount].ColumnName.ToString();
for (int cCount = 0; cCount <= inputTable.Rows.Count - 1; cCount++)
{
string colValue = inputTable.Rows[cCount][rCount].ToString();
newRow[cCount + 1] = colValue;
}
outputTable.Rows.Add(newRow);
}
return outputTable;
}
For example in the intellisense output shown below the row for improved, where the values after contain no data (this would normally be numeric values) instead contains empty indexes:
I need to be able to delete these rows if they are in the above format, how can I modify my code to perform this?
Why not set a condition which prevents adding the row if all the row cells have a null value?
if (newRow.ItemArray.Any(x => x != null))
{
outputTable.Rows.Add(newRow);
}
If you need to check for columns as well, do this right before returning outputTable
for (int col = outputTable.Columns.Count - 1; col >= 0; col--)
{
bool toDelete = true;
for (int row = 0; row < outputTable.Rows.Count; row++)
{
if (outputTable.Rows[row][col] != null)
{
toDelete = false;
}
}
if (toDelete)
{
outputTable.Columns.RemoveAt(col);
}
}
You can try with something like this (comments are in code):
private void CheckColumns()
{
//table which we want to check
DataTable table = new DataTable();
//add column definition - first column will be string, other two are int columns
table.Columns.Add("string column", typeof(string));
table.Columns.Add("int column 1", typeof(int));
table.Columns.Add("int column 2", typeof(int));
//add data - in this example rows "abc" and "ghi" are valid because they have at least one numeric column
table.Rows.Add(new object[] { "abc", 1, 2 });
table.Rows.Add(new object[] { "def", null, null });
table.Rows.Add(new object[] { "ghi", null, 2 });
table.Rows.Add(new object[] { "jkl", null, null });
//filter rows in a way, using Linq, that rows are filtered where at least one column has numeric value
var validRows = table.AsEnumerable().Where(r => r.ItemArray.Any(c => IsNumeric(c))).ToList();
}
//this is helper method that code will call for each value in each row
private bool IsNumeric(object value)
{
int outputValue;
return int.TryParse(value.ToString(), out outputValue);
}
If you'll have decimal values, then you should une decimal.TyrParse in IsNumeric method.
If you need to be sure that all columns except first one have numeric values, you can do it like this (skipping first value from each row and checking if all other values are numeric)...
var validRows = table.AsEnumerable().Where(r => r.ItemArray.Skip(1).All(c => IsNumeric(c))).ToList();
once you have those 'valid' rows, you can write that data into another table or do whatever you need to do with those data...
Instead of .ToList() you can use .CopyToDataTable() method so you'll get new DataTable with those 'valid' rows. For example:
DataTable newDataTable = table.AsEnumerable().Where(r => r.ItemArray.Skip(1).All(c => IsNumeric(c))).CopyToDataTable();
I'm having some problem while trying to set column value.
I'v had a dataTable which get some values from SQL and then im adding two new columns by :
dataTable.Columns.Add("dest", typeof(int));
dataTable.Columns.Add("amount", typeof(int));
Which works great but now i want to put 0 in every row in column name dest - and later user will edit this, and then i want to set amount value as
amount = all(this column is in dataTable before I add these 2 columns) + dest;
int columnNumber = 5; //Put your column X number here
for (int i = 0; i < yourDataTable.Rows.Count; i++)
{
yourDataTable.Rows[i][columnNumber] = "0";
}
You can use foreach too.
foreach (DataRow row in myDataTable.Rows)
//if (row["X"] has condition) // or if any condition
row["colName"] = row[colIndex] = "abc";
I have a datatable containing over 100 columns, how ever I need to strip out all columns
except first 11 columns.
I need to retain data of 1st 11 columns.
I am doing it with following code
public DataTable validdatatable(DataTable table)
{
DataTable dt = new DataTable();
for (int i = 0; i < 11; i++)
{
DataColumn dc = new DataColumn();
dc.ColumnName = table.Columns[i].ColumnName;
dc.DataType = table.Columns[i].DataType;
dt.Columns.Add(dc);
}
for (int i = 0; i < table.Rows.Count; i++)
{
object[] ob = table.Rows[i].ItemArray;
...
...
}
return dt;
}
This methods works but is too heavy on CPU and Ram.
Is there any other method with which I can proceed?
Try this:
public DataTable validdatatable(DataTable table)
{
var dt = table.Columns.Cast<DataColumn>().Take(11);
return dt.CopyToDataTable();
}
Or Something like this. It will give you at least a way to work on it.
Note that You need to add a reference to the assembly: System.Data.DataSetExtensions.dll then you can write your function like above.
You can try this. The only difference would be instead of object[] ob = table.Rows[i].ItemArray it will just grab the first 11 columns using the index and make an array out of that (itemArray will make an array of all 100 columns). Still doubt this will solve your memory issues if you are that tight but it's probably worth a shot.
var copyDt = new DataTable();
for (var i = 0; i < 11; i++)
{
copyDt.Columns.Add(dataTable.Columns[i].ColumnName, dataTable.Columns[1].DataType);
}
copyDt.BeginLoadData();
foreach (DataRow dr in dataTable.Rows)
{
copyDt.Rows.Add(Enumerable.Range(0, 11).Select(i => dr[i]).ToArray());
}
copyDt.EndLoadData();
How to use Datarow to retrieve data based on column name? I am trying to loop the db data from my first looping
//Trying to get data
DataRow dr = dsResult.Tables[1].Rows[0];
//trying to get data successful
//what i trying to achieve is to retrieve data from database based on rows index and
column name
for(int i =0; i <datagridview.Rows.Count ; i++){
string a = dr['ColumnName'].['RowsIndex'].toString(); //Failed
}
for (int i = 0; i < dataTable.Rows.Count; i++)
{
DataRow dr = dataTable.Rows[i]; //Where the RowIndex
string a = dr[0].ToString(); //Where the ColumnIndex or ColumnName
}
Try ?
dr.Rows[RowsIndex]['ColumnName'].ToString()
Have you tried removing the period after the 'columnName' specification, and putting rows[i]["columnName"] rather than [columnName][rows]?