How to: Set GridView Web Server Control Column Width Dynamically

Artigo
10/15/2014

By default, columns in the GridView control are sized automatically. Columns render as HTML table cells (td elements) without width information; most browsers size table cells to allow for the widest content in the column.

If it is required, you can set the width of individual columns in the GridView control programmatically. This is useful, if the width of the column depends on information that is available only at run time. For example, you might size a column according to its contents—that is, based on the data that the GridView control binds to.

The basic technique for setting column width involves setting the Width property of a column template. If you want the width to be set according to its contents, you can handle the RowDataBound event. This makes the data for a row available to you for examination.

To set column width dynamically

In code, set the Width property of the ItemStyle property for a GridView control column to the width that you want.

The following code example shows how to set the width of all the columns in the GridView1 control to the value that a user enters in a text box.

Protected Sub Button1_Click(ByVal sender As Object, _
        ByVal e As System.EventArgs)
    Try
      Dim colWidth As Integer
      colWidth = CInt(Server.HtmlEncode(TextBox1.Text))
      If colWidth > 0 Then
        For i As Integer = 0 To GridView1.Columns.Count - 1
          GridView1.Columns(i).ItemStyle.Width = colWidth
        Next
      End If
    Catch
      ' Report error.
    End Try
End Sub

protected void Button1_Click(object sender, EventArgs e)
{
    try
    {
      int colWidth = Int16.Parse(Server.HtmlEncode(TextBox1.Text));
      if (colWidth > 0)
      {
        for (int i = 0; i < GridView1.Columns.Count; i++)
        {
          GridView1.Columns[i].ItemStyle.Width = colWidth;
        }
      }
    }
    catch
    {
      // Report error.      
    }
}

To set column width based on data contents

Create a handler for the RowDataBound event.

The RowDataBound event is raised each time that a new row is data-bound in the grid and gives you access to the data for each row.

In the event handler, do the following:

Create a DataRowView object and assign to it the DataItem value for the current grid row.

The DataItem property is typed as an object. Therefore, you must cast it.
Test for a data row (DataControlRowType) to make sure that you are working with a data-bound row and not a header or footer.
From the DataRowView object, extract the data value that you want to examine.
Set the Width property for the ItemStyle property.
Set the Wrap property of the ItemStyle property to false.

If the Wrap property is false, the column is automatically resized.

The following code example shows how to set the width of a column (in this case, the third column) based on the width of the widest data element of the second column. The RowDataBound event handler is called one time for each data row that is displayed by the GridView control. The code stores the character count of the widest element in a protected page member. The code sets the width of the column to the character count times 30 (an arbitrary multiplier).

Protected widestData As Integer
Protected Sub GridView1_RowDataBound(ByVal sender As Object, _
        ByVal e As System.Web.UI.WebControls.GridViewRowEventArgs)
    Dim drv As System.Data.DataRowView
    drv = CType(e.Row.DataItem, System.Data.DataRowView)
    If e.Row.RowType = DataControlRowType.DataRow Then
      If drv IsNot Nothing Then
        Dim catName As String = drv(1).ToString()
        Dim catNameLen As Integer = catName.Length
        If catNameLen > widestData Then
          widestData = catNameLen
          GridView1.Columns(2).ItemStyle.Width = _
              widestData * 30
          GridView1.Columns(2).ItemStyle.Wrap = False
        End If
      End If
    End If
End Sub

Protected Sub Page_Load(ByVal sender As Object, _
        ByVal e As System.EventArgs) Handles Me.Load
    widestData = 0
End Sub

protected int widestData;
protected void GridView1_RowDataBound(object sender, 
    GridViewRowEventArgs e)
{
    System.Data.DataRowView drv;
    drv = (System.Data.DataRowView)e.Row.DataItem;
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
      if (drv != null)
      {
        String catName = drv[1].ToString();
        Response.Write(catName + "/");

        int catNameLen = catName.Length;
        if (catNameLen > widestData)
        {
          widestData = catNameLen;
          GridView1.Columns[2].ItemStyle.Width =
            widestData * 30;
          GridView1.Columns[2].ItemStyle.Wrap = false;
        }

      }
    }
}

protected void Page_Load(object sender, EventArgs e)
{
    widestData = 0;
}

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How to: Set GridView Web Server Control Column Width Dynamically

To set column width dynamically

To set column width based on data contents

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