如何在 C# 中将 DataTable 转换为字符串？

Question

I'm using Visual Studio 2005 and have a DataTable with two columns and some rows that I want to output to the console. I hoped there would be something like:

DataTable results = MyMethod.GetResults();
Console.WriteLine (results.ToString());

What's the best way (ie least amount of coding from me) to convert a simple DataTable to a string?

Answer 1

Prerequisite

using System.Linq;

then...

string res = string.Join(Environment.NewLine, 
    results.Rows.OfType<DataRow>().Select(x => string.Join(" ; ", x.ItemArray)));

Answer 2

Late but this is what I use

 public static string ConvertDataTableToString(DataTable dataTable)
    {
        var output = new StringBuilder();

        var columnsWidths = new int[dataTable.Columns.Count];

        // Get column widths
        foreach (DataRow row in dataTable.Rows)
        {
           for(int i = 0; i < dataTable.Columns.Count; i++)
           {
               var length = row[i].ToString().Length;
               if (columnsWidths[i] < length)
                   columnsWidths[i] = length;
           }     
        }

        // Get Column Titles
        for (int i = 0; i < dataTable.Columns.Count; i++)
        {
            var length = dataTable.Columns[i].ColumnName.Length;
               if (columnsWidths[i] < length)
                   columnsWidths[i] = length;
        }

        // Write Column titles
        for (int i = 0; i < dataTable.Columns.Count; i++)
        {
            var text = dataTable.Columns[i].ColumnName;
            output.Append("|" + PadCenter(text, columnsWidths[i] + 2));
        }
        output.Append("|\n" + new string('=', output.Length) + "\n");

        // Write Rows
        foreach (DataRow row in dataTable.Rows)
        {
            for (int i = 0; i < dataTable.Columns.Count; i++)
            {
                var text = row[i].ToString();
                output.Append("|" + PadCenter(text,columnsWidths[i] + 2));
            }
            output.Append("|\n");
        }
        return output.ToString();
    }

    private static string PadCenter(string text, int maxLength)
    {
        int diff = maxLength - text.Length;
        return new string(' ', diff/2) + text + new string(' ', (int) (diff / 2.0 + 0.5));

    } 

Answer 3

using(var writer = new StringWriter()) {
    results.WriteXml(writer);
    Console.WriteLine(writer.ToString());
}

Of course the usefulness of this depends on how important the formatting is. If it's just a debug dump, I find XML outputs like this very readable. However, if the formatting is important to you, then you have no choice but to write your own method to do it.

Answer 4

You could use something like this :

Private Sub PrintTableOrView(ByVal table As DataTable, ByVal label As String)
    Dim sw As System.IO.StringWriter
    Dim output As String

    Console.WriteLine(label)

    ' Loop through each row in the table. '
    For Each row As DataRow In table.Rows
        sw = New System.IO.StringWriter
        ' Loop through each column. '
        For Each col As DataColumn In table.Columns
            ' Output the value of each column's data.
            sw.Write(row(col).ToString() & ", ")
        Next
        output = sw.ToString
        ' Trim off the trailing ", ", so the output looks correct. '
        If output.Length > 2 Then
            output = output.Substring(0, output.Length - 2)
        End If
        ' Display the row in the console window. '
        Console.WriteLine(output)
    Next
    Console.WriteLine()
End Sub

Answer 5

i know i'm years late xD but Here's how i did it

    public static string convertDataTableToString(DataTable dataTable)
    {
        string data = string.Empty;
        for (int i = 0; i < dataTable.Rows.Count; i++)
        {
            DataRow row = dataTable.Rows[i];
            for (int j = 0; j < dataTable.Columns.Count; j++)
            {
                data += dataTable.Columns[j].ColumnName + "~" + row[j];
                if (j == dataTable.Columns.Count - 1)
                {
                    if (i != (dataTable.Rows.Count - 1))
                        data += "$";
                }
                else
                    data += "|";
            }
        }
        return data;
    }

If someone ever optimizes this please let me know

i tried this:

    public static string convertDataTableToString(DataTable dataTable)
    {
        string data = string.Empty;
        int rowsCount = dataTable.Rows.Count;
        for (int i = 0; i < rowsCount; i++)
        {
            DataRow row = dataTable.Rows[i];
            int columnsCount = dataTable.Columns.Count;
            for (int j = 0; j < columnsCount; j++)
            {
                data += dataTable.Columns[j].ColumnName + "~" + row[j];
                if (j == columnsCount - 1)
                {
                    if (i != (rowsCount - 1))
                        data += "$";
                }
                else
                    data += "|";
            }
        }
        return data;
    }

but this answer says it's worse

Answer 6

I would install PowerShell . It understands .NET objects and has an Format-Table and Export-Csv that would do exactly what you are looking for. If you do any sort of console work it is a great complement/replacement to C# console apps.

When I started using it, I rewrote my console apps as libraries and import the libraries into Powershell. The built-in commandlets make console work so nice.

Answer 7

two for loops, one for rows, another for columns, output dataRow(i).Value. Watch out for nulls and DbNulls.

Answer 8

public static string DataTable2String(DataTable dataTable)
{
    StringBuilder sb = new StringBuilder();
    if (dataTable != null)
    {
        string seperator = " | ";

        #region get min length for columns
        Hashtable hash = new Hashtable();
        foreach (DataColumn col in dataTable.Columns)
            hash[col.ColumnName] = col.ColumnName.Length;
        foreach (DataRow row in dataTable.Rows)
            for (int i = 0; i < row.ItemArray.Length; i++)
                if (row[i] != null)
                    if (((string)row[i]).Length > (int)hash[dataTable.Columns[i].ColumnName])
                        hash[dataTable.Columns[i].ColumnName] = ((string)row[i]).Length;
        int rowLength = (hash.Values.Count + 1) * seperator.Length;
        foreach (object o in hash.Values)
            rowLength += (int)o;
        #endregion get min length for columns

        sb.Append(new string('=', (rowLength - " DataTable ".Length) / 2));
        sb.Append(" DataTable ");
        sb.AppendLine(new string('=', (rowLength - " DataTable ".Length) / 2));
        if (!string.IsNullOrEmpty(dataTable.TableName))
            sb.AppendLine(String.Format("{0,-" + rowLength + "}", String.Format("{0," + ((rowLength + dataTable.TableName.Length) / 2).ToString() + "}", dataTable.TableName)));

        #region write values
        foreach (DataColumn col in dataTable.Columns)
            sb.Append(seperator + String.Format("{0,-" + hash[col.ColumnName] + "}", col.ColumnName));
        sb.AppendLine(seperator);
        sb.AppendLine(new string('-', rowLength));
        foreach (DataRow row in dataTable.Rows)
        {
            for (int i = 0; i < row.ItemArray.Length; i++)
            {
                sb.Append(seperator + String.Format("{0," + hash[dataTable.Columns[i].ColumnName] + "}", row[i]));
                if (i == row.ItemArray.Length - 1)
                    sb.AppendLine(seperator);
            }
        }
        #endregion write values

        sb.AppendLine(new string('=', rowLength));
    }
    else
        sb.AppendLine("================ DataTable is NULL ================");

    return sb.ToString();
}

output:

======================= DataTable =======================
                         MyTable                          
 | COL1 | COL2                    | COL3 1000000ng name | 
----------------------------------------------------------
 |    1 |                       2 |                   3 | 
 |  abc | Dienstag, 12. März 2013 |                 xyz | 
 | Have |                  a nice |                day! | 
==========================================================

Answer 9

    /// <summary>
    /// Dumps the passed DataSet obj for debugging as list of html tables
    /// </summary>
    /// <param name="msg"> the msg attached </param>
    /// <param name="ds"> the DataSet object passed for Dumping </param>
    /// <returns> the nice looking dump of the DataSet obj in html format</returns>
    public static string DumpHtmlDs(string msg, ref System.Data.DataSet ds)
    {
        StringBuilder objStringBuilder = new StringBuilder();
        objStringBuilder.AppendLine("<html><body>");

        if (ds == null)
        {
            objStringBuilder.AppendLine("Null dataset passed ");
            objStringBuilder.AppendLine("</html></body>");
            WriteIf(objStringBuilder.ToString());
            return objStringBuilder.ToString();
        }

        objStringBuilder.AppendLine("<p>" + msg + " START </p>");
        if (ds != null)
        {
            if (ds.Tables == null)
            {
                objStringBuilder.AppendLine("ds.Tables == null ");
                return objStringBuilder.ToString();
            }


            foreach (System.Data.DataTable dt in ds.Tables)
            {

                if (dt == null)
                {
                    objStringBuilder.AppendLine("ds.Tables == null ");
                    continue;
                }
                objStringBuilder.AppendLine("<table>");

                //objStringBuilder.AppendLine("================= My TableName is  " +
                //dt.TableName + " ========================= START");
                int colNumberInRow = 0;
                objStringBuilder.Append("<tr><th>row number</th>");
                foreach (System.Data.DataColumn dc in dt.Columns)
                {
                    if (dc == null)
                    {
                        objStringBuilder.AppendLine("DataColumn is null ");
                        continue;
                    }


                    objStringBuilder.Append(" <th> |" + colNumberInRow.ToString() + " | ");
                    objStringBuilder.Append(  dc.ColumnName.ToString() + " </th> ");
                    colNumberInRow++;
                } //eof foreach (DataColumn dc in dt.Columns)
                objStringBuilder.Append("</tr>");

                int rowNum = 0;
                foreach (System.Data.DataRow dr in dt.Rows)
                {
                    objStringBuilder.Append("<tr><td> row - | " + rowNum.ToString() + " | </td>");
                    int colNumber = 0;
                    foreach (System.Data.DataColumn dc in dt.Columns)
                    {
                        objStringBuilder.Append(" <td> |" + colNumber + "|" );
                        objStringBuilder.Append(dr[dc].ToString() + "  </td>");
                        colNumber++;
                    } //eof foreach (DataColumn dc in dt.Columns)
                    rowNum++;
                    objStringBuilder.AppendLine(" </tr>");
                }   //eof foreach (DataRow dr in dt.Rows)

                objStringBuilder.AppendLine("</table>");
                objStringBuilder.AppendLine("<p>" + msg + " END </p>");
            }   //eof foreach (DataTable dt in ds.Tables)

        } //eof if ds !=null 
        else
        {

            objStringBuilder.AppendLine("NULL DataSet object passed for debugging !!!");
        }
        return objStringBuilder.ToString();

    } 

Answer 10

very vague....

id bung it into a dataset simply so that i can output it easily as xml....

failing that why not iterate through its row and column collections and output them?

Answer 11

Or, change the app to WinForms, use grid and bind DataTable to grid. If it is a demo/sample app.

Answer 12

I created my variant of class for your needs. I believe it is a bit more configurable than already provided variants. You can use it with all default settings just create an instance of a class and call StringifyDataTable method, or you can set additional options if needed.

public class DataTableStringifier
{
    public bool IsOuterBordersPresent { get; set; } //Whether outer borders of table needed
    public bool IsHeaderHorizontalSeparatorPresent { get; set; } // Whether horizontal line separator between table title and data is needed. Useful to set 'false' if you expect only 1 or 2 rows of data - no need for additional lines then
    public char ValueSeparator { get; set; } //Vertical line character
    public char HorizontalLinePadChar { get; set; } // Horizontal line character
    public char HorizontalLineSeparator { get; set; } // Horizontal border (between header and data) column separator (crossing of horizontal and vertical borders)
    public int ValueMargin { get; set; } // Horizontal margin from table borders (inner and outer) to cell values
    public int MaxColumnWidth { get; set; } // To avoid too wide columns with thousands of characters. Longer values will be cropped in the center
    public string LongValuesEllipses { get; set; } // Cropped values wil be inserted this string in the middle to mark the point of cropping

    public DataTableStringifier()
    {
        MaxColumnWidth = int.MaxValue;
        IsHeaderHorizontalSeparatorPresent = true;
        ValueSeparator = '|';
        ValueMargin = 1;
        HorizontalLinePadChar = '-';
        HorizontalLineSeparator = '+';
        LongValuesEllipses = "...";
        IsOuterBordersPresent = false;
    }

    public string StringifyDataTable(DataTable table)
    {
        int colCount = table.Columns.Count;
        int rowCount = table.Rows.Count;
        string[] colHeaders = new string[colCount];
        string[,] cells = new string[rowCount, colCount];
        int[] colWidth = new int[colCount];

        for (int i = 0; i < colCount; i++)
        {
            var column = table.Columns[i];
            var colName = ValueToLimitedLengthString(column.ColumnName);
            colHeaders[i] = colName;
            if (colWidth[i] < colName.Length)
            {
                colWidth[i] = colName.Length;
            }
        }

        for (int i = 0; i < rowCount; i++)
        {
            DataRow row = table.Rows[i];
            for (int j = 0; j < colCount; j++)
            {
                var valStr = ValueToLimitedLengthString(row[j]);
                cells[i, j] = valStr;
                if (colWidth[j] < valStr.Length)
                {
                    colWidth[j] = valStr.Length;
                }
            }
        }

        string valueSeparatorWithMargin = string.Concat(new string(' ', ValueMargin), ValueSeparator, new string(' ', ValueMargin));
        string leftBorder = IsOuterBordersPresent ? string.Concat(ValueSeparator, new string(' ', ValueMargin)) : "";
        string rightBorder = IsOuterBordersPresent ? string.Concat(new string(' ', ValueMargin), ValueSeparator) : "";
        string horizLine = new string(HorizontalLinePadChar, colWidth.Sum() + (colCount - 1)*(ValueMargin*2 + 1) + (IsOuterBordersPresent ? (ValueMargin + 1)*2 : 0));

        StringBuilder tableBuilder = new StringBuilder();

        if (IsOuterBordersPresent)
        {
            tableBuilder.AppendLine(horizLine);
        }

        tableBuilder.Append(leftBorder);
        for (int i = 0; i < colCount; i++)
        {
            tableBuilder.Append(colHeaders[i].PadRight(colWidth[i]));
            if (i < colCount - 1)
            {
                tableBuilder.Append(valueSeparatorWithMargin);
            }
        }
        tableBuilder.AppendLine(rightBorder);

        if (IsHeaderHorizontalSeparatorPresent)
        {
            if (IsOuterBordersPresent)
            {
                tableBuilder.Append(ValueSeparator);
                tableBuilder.Append(HorizontalLinePadChar, ValueMargin);
            }
            for (int i = 0; i < colCount; i++)
            {
                tableBuilder.Append(new string(HorizontalLinePadChar, colWidth[i]));
                if (i < colCount - 1)
                {
                    tableBuilder.Append(HorizontalLinePadChar, ValueMargin);
                    tableBuilder.Append(HorizontalLineSeparator);
                    tableBuilder.Append(HorizontalLinePadChar, ValueMargin);
                }
            }
            if (IsOuterBordersPresent)
            {
                tableBuilder.Append(HorizontalLinePadChar, ValueMargin);
                tableBuilder.Append(ValueSeparator);
            }
            tableBuilder.AppendLine();
        }

        for (int i = 0; i < rowCount; i++)
        {
            tableBuilder.Append(leftBorder);
            for(int j=0; j<colCount; j++)
            {
                tableBuilder.Append(cells[i, j].PadRight(colWidth[j]));
                if(j<colCount-1)
                {
                    tableBuilder.Append(valueSeparatorWithMargin);
                }
            }
            tableBuilder.AppendLine(rightBorder);
        }

        if (IsOuterBordersPresent)
        {
            tableBuilder.AppendLine(horizLine);
        }

        return tableBuilder.ToString(0, tableBuilder.Length - 1); //Trim last enter char
    }

    private string ValueToLimitedLengthString(object value)
    {
        string strValue = value.ToString();
        if (strValue.Length > MaxColumnWidth)
        {
            int beginningLength = (MaxColumnWidth) / 2;
            int endingLength = (MaxColumnWidth + 1) / 2 - LongValuesEllipses.Length;
            return string.Concat(strValue.Substring(0, beginningLength), LongValuesEllipses, strValue.Substring(strValue.Length - endingLength, endingLength));
        }
        else
        {
            return strValue;
        }
    }
}

Answer 13

If you have a single column in datatable than it's simple to change datatable to string .

DataTable results = MyMethod.GetResults();
if(results != null && results.Rows.Count > 0)  // Check datatable is null or not
{
  List<string> lstring = new List<string>();
  foreach(DataRow dataRow in dt.Rows)
  {
     lstring.Add(Convert.ToString(dataRow["ColumnName"]));
  }
  string mainresult = string.Join(",", lstring.ToArray()); // You can Use comma(,) or anything which you want. who connect the two string. You may leave space also.
}
Console.WriteLine (mainresult);