void gridView_RowDataBound(object sender, GridViewRowEventArgs e)
{
    if(e.Row.RowType == DataControlRowType.DataRow)
    {
      DropDownList ddl = (DropDownList)e.Row.Cells[x].FindControl(dropDownList); // Cells[x]就是包含了dropdownlist控件的哪个列
       ddl.SelectedValue = DataBinder.Eval(e.Row.DataItem, "列名").ToString();
      // 或者：
       // DataRowView drv = (DataRowView)e.Row.DataItem;
      // ddl.SelectedValue = drv["列名"].ToString();
    }

}

------解决方案--------------------
C# code
属性=<%#Eval("catalogue")%>

------解决方案--------------------
给你个参考：
protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{	
 if (e.Row.RowType == DataControlRowType.DataRow)
 {
   System.Data.DataRowView drv = (System.Data.DataRowView)e.Row.DataItem;    RadioButtonList rbl = (RadioButtonList)e.Row.FindControl("txtGender");
   if (rbl != null)
   {
     if ((bool)drv["Gender"])
     {
       rbl.Items.FindByText("男").Selected = true;
     }
     else
     {
       rbl.Items.FindByText("女").Selected = true;
     }
   }

   DropDownList ddl = (DropDownList)e.Row.FindControl("txtClassName");
   if (ddl != null)
   {
     ddl.Items.FindByText(drv["ClassName"].ToString()).Selected = true;
   }
 }
}


------解决方案--------------------
protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)  
{  
 if (e.Row.RowType == DataControlRowType.DataRow)  
 {  
   System.Data.DataRowView drv = (System.Data.DataRowView)e.Row.DataItem;    RadioButtonList rbl = (RadioButtonList)e.Row.FindControl("txtGender");  
   if (rbl != null)  
   {  
     if ((bool)drv["Gender"])  
     {  
       rbl.Items.FindByText("男").Selected = true;  
     }  
     else  
     {  
       rbl.Items.FindByText("女").Selected = true;  
     }  
   }  

   DropDownList ddl = (DropDownList)e.Row.FindControl("txtClassName");  
   if (ddl != null)  
   {  
     ddl.Items.FindByValue(drv["ClassID"].ToString()).Selected = true; ///这是根据VALUE查找
   }  
 }  
}  
请参考：ListItemCollection.FindByText（FindByValue) Method

------解决方案--------------------
我写过ComboBox的例子，和DropDownList差不多的，你借鉴一下：
//创建一个DataTable用于数据源
DataTable dt = new DataTable("TestTable");
dt.Columns.Add("Col1", typeof(int));
dt.Columns.Add("Col2", typeof(string));           
dt.Rows.Add(1, "aaa");
dt.Rows.Add(2, "bbb");

//绑定的过程
DataGridViewComboBoxColumn cmbColumn = new DataGridViewComboBoxColumn();
cmbColumn.DataSource = dt; // bound ComboBox to a data source
cmbColumn.DisplayMember = "Col1"; //the property of the data source for the ComboBox to show