C#数据库工具开发（八）

问题（07/19）

1. 如何实现拖拽文件到textbox获取文件路径？

利用textbox两个事件：dragenter和dragdrop
具体实现

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private void filePath_DragEnter(object sender, DragEventArgs e)
   {
       if (e.Data.GetDataPresent(DataFormats.FileDrop))
       {
           e.Effect = DragDropEffects.Link;
       }
       else
       {
           e.Effect = DragDropEffects.None;
       }
   }
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private void filePath_DragDrop(object sender, DragEventArgs e)
{
string path = ((System.Array)e.Data.GetData(DataFormats.FileDrop)).GetValue(0).ToString();
        filePath.Text = path;
}

2. 数据库如何增删改字段？

只考虑SQLServer和Oracle，增加和删除字段可用相同sql语句,修改字段略有不同：

增加：
sql = @"use " + DBName + "; ALTER TABLE " + tableName + " ADD " + fieldName + " " + fieldType + "(" + fieldLength + ");";

删除：
sql = @"use " + DBName + "; ALTER TABLE " + tableName + " DROP COLUMN " + fieldName + ";";

修改：

SQLSerer：sql = @"use " + DBName + "; ALTER TABLE " + tableName + " ALTER COLUMN " + fieldName + " " + fieldType + "(" + fieldLength + ");";

Oracle:sql = @"ALTER TABLE " + tableName + " modify(" + fieldName + " " + fieldType + "(" + fieldLength + "))";

3. 如何导出文件？

使用SaveFileDialog控件

具体实现：

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SaveFileDialog saveFileDialog1 = new SaveFileDialog();
      saveFileDialog1.Filter = "TXT|*.txt";
      saveFileDialog1.Title = "选择导出sql记录的存储路径";
      saveFileDialog1.ShowDialog();

      // If the file name is not an empty string open it for saving.  
      if (saveFileDialog1.FileName != "")
      {
          // Saves the Image via a FileStream created by the OpenFile method.  
          System.IO.FileStream fs =
             (System.IO.FileStream)saveFileDialog1.OpenFile();
          // Saves the Image in the appropriate ImageFormat based upon the  
          // File type selected in the dialog box.  
          // NOTE that the FilterIndex property is one-based.  
          StreamWriter sw = new StreamWriter(fs);
          foreach(string result in sqlcommands)
          {
              sw.WriteLine(result);
          }

          //清空缓冲区
          sw.Flush();
          //关闭流
          sw.Close();
          
          fs.Close();
      }

4. 如何给DataGridView增加行号

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private void dataXML_RowPostPaint(object sender, DataGridViewRowPostPaintEventArgs e)
    {
        var grid = sender as DataGridView;
        var rowIdx = (e.RowIndex + 1).ToString();

        var centerFormat = new StringFormat()
        {
            // right alignment might actually make more sense for numbers
            Alignment = StringAlignment.Center,
            LineAlignment = StringAlignment.Center
        };

        var headerBounds = new Rectangle(e.RowBounds.Left, e.RowBounds.Top, grid.RowHeadersWidth, e.RowBounds.Height);
        e.Graphics.DrawString(rowIdx, this.Font, SystemBrushes.ControlText, headerBounds, centerFormat);
    }