用Datagrid控件显示表格数据，当表格内容过多时，Datagrid控件单元格宽度并不足以用来完全显示表格中的数据内容。而只有自己每次去拉动分界线，来进行调整。当出现表格字段比较多时，这样做就显得很麻烦。
以下是用程序根据表格内容来自动调整Datagrid控件单元格宽度。
先定义一个Sub过程AutoSizeCol，用来调整Datagrid中的列宽。
如下：
Public Sub AutoSizeCol(ByVal col As Integer)
Dim width As Single
width = 0
Dim numRows As Integer
numRows = CType(dataGrid1.DataSource, DataTable).Rows.Count
Dim g As Graphics
g = Graphics.FromHwnd(dataGrid1.Handle)
Dim sf As StringFormat
sf = New StringFormat(StringFormat.GenericTypographic)
Dim size As SizeF
Dim i As Integer
i = 0

Do While (i < numRows)
size = g.MeasureString(dataGrid1(i, col).ToString, dataGrid1.Font, 500, sf)
If (size.Width > width) Then
width = size.Width
End If
i = (i + 1)
Loop

g.Dispose()
dataGrid1.TableStyles("customers").GridColumnStyles(col).Width = CType(width, Integer)

End Sub

现在就可以表格内容来定义整张表所有列的宽度了。如下：
Public Sub AutoSizeTable()
Dim numCols As Integer
numCols = CType(dataGrid1.DataSource, DataTable).Columns.Count
Dim i As Integer
i = 0
Do While (i < numCols)
AutoSizeCol(i)
i = (i + 1)
Loop
End Sub

只要使用以上两个Sub过程就可以达到你想要的结果了！

一个完整的实例如下:
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim connString As String
connString = "Provider=Microsoft.JET.OLEDB.4.0;data source=northwind.mdb"
Dim sqlString As String
sqlString = "SELECT * FROM customers"
Dim dataAdapter As OleDbDataAdapter
dataAdapter = Nothing
Dim _dataSet As DataSet
_dataSet = Nothing

Try

Dim connection As OleDbConnection
connection = New OleDbConnection(connString)

dataAdapter = New OleDbDataAdapter(sqlString, connection)

_dataSet = New DataSet
dataAdapter.Fill(_dataSet, "customers")
connection.Close()
Catch ex As Exception
MessageBox.Show("出错！")
Me.Close()
Return
End Try
Dim tableStyle As DataGridTableStyle
tableStyle = New DataGridTableStyle
tableStyle.MappingName = "customers"

dataGrid1.TableStyles.Clear()
dataGrid1.TableStyles.Add(tableStyle)
dataGrid1.DataSource = _dataSet.Tables("customers")
End Sub

Private Sub button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles button1.Click
AutoSizeTable()
End Sub

Private Sub button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles button2.Click
AutoSizeCol(1)
End Sub