Resizing Data Grid Columns To Content

Environment: .NET, C#

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Demo application to test datagrid resizing method

Introduction

One peculiar omission from the Windows Forms teams regarding the DataGrid object is a method that enables you to resize the grid's columns to visually accomodate the width of its widest data value. This method gives you that ability.

Acknowledgements

Using the Code

Syntax

Calling this method is very straightforward. It takes only two parameters:

public void SizeColumnsToContent(DataGrid dataGrid,
                                 int nRowsToScan)

• dataGrid—The DataGrid object to be resized
• nRowsToScan—The number of rows to scan when searching for the widest value for a given column. Passing a value of -1 indicates that all rows should be scanned.

Notes

• In my own code, I have defined a method as a member of my own System.Windows.Forms.DataGrid-derived class (DataGridEx). I removed it from that class for this article to keep things simple. To use the method in the same manner that I did, simply remove the dataGrid parameter from the parameter list and replace the references to dataGrid with reference to the this object.
• The reason for the nRowsToScan parameter is for performance issues regarding very large amounts of data. If you happen to have a datagrid with a large number of rows, you can simply have the grid's columns sized according to the widest column of the first n rows instead of the method iterating through the entire data set for each column.

SizeColumnsToContent Method

public void SizeColumnsToContent(DataGrid dataGrid,
       int nRowsToScan)
{
  // Create graphics object for measuring widths.
  Graphics Graphics = dataGrid.CreateGraphics();

  // Define new table style.
  DataGridTableStyle tableStyle = new DataGridTableStyle();

  try
  {
    DataTable dataTable = (DataTable)dataGrid.DataSource;

    if (-1 == nRowsToScan)
    {
      nRowsToScan = dataTable.Rows.Count;
    }
    else
    {
      // Can only scan rows if they exist.
      nRowsToScan = System.Math.Min(nRowsToScan,
                    dataTable.Rows.Count);
    }

    // Clear any existing table styles.
    dataGrid.TableStyles.Clear();

    // Use mapping name that is defined in the data source.
    tableStyle.MappingName = dataTable.TableName;

    // Now create the column styles within the table style.
    DataGridTextBoxColumn columnStyle;
    int iWidth;

    for (int iCurrCol = 0;
         iCurrCol < dataTable.Columns.Count; iCurrCol++)
    {
      DataColumn dataColumn = dataTable.Columns[iCurrCol];

      columnStyle = new DataGridTextBoxColumn();

      columnStyle.TextBox.Enabled = true;
      columnStyle.HeaderText = dataColumn.ColumnName;
      columnStyle.MappingName = dataColumn.ColumnName;

      // Set width to header text width.
      iWidth = (int)(Graphics.MeasureString
                    (columnStyle.HeaderText,
                     dataGrid.Font).Width);

      // Change width, if data width is
      // wider than header text width.
      // Check the width of the data in the first X rows.
      DataRow dataRow;
      for (int iRow = 0; iRow < nRowsToScan; iRow++)
      {
        dataRow = dataTable.Rows[iRow];

        if (null != dataRow[dataColumn.ColumnName])
        {
          int iColWidth = (int)(Graphics.MeasureString
                          (dataRow.ItemArray[iCurrCol].ToString(),
                           dataGrid.Font).Width);
          iWidth = (int)System.Math.Max(iWidth, iColWidth);
        }
      }
      columnStyle.Width = iWidth + 4;

      // Add the new column style to the table style.
      tableStyle.GridColumnStyles.Add(columnStyle);
    }
    // Add the new table style to the data grid.
    dataGrid.TableStyles.Add(tableStyle);
  }
  catch(Exception e)
  {
    MessageBox.Show(e.Message);
  }
  finally
  {
    Graphics.Dispose();
  }
}

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