如何将按钮添加到现有列并显示在整行中

Question

我正在使用GridView我需要在现有列中添加按钮（将现有列转换为按钮列）不使用按钮添加新列。我的专栏名为Volunteers。

请参阅以下代码：

    public void showCourse()
    {
        SqlCommand com = new SqlCommand("SELECT [Course_ID],[Course_Name],[Course_Type],[Course_Hours],[Course_Duration],[Course_Place],[Trainer_ID],[Volunteers] FROM [VolunteersAffairs].[dbo].[Course_Info]", con);
        SqlDataAdapter da = new SqlDataAdapter();
        DataSet dats = new DataSet();
        da.SelectCommand = com;
        da.Fill(dats, "Course_Info");
        dataGridViewShowCourse.DataSource = dats.Tables["Course_Info"];
        DataGridViewButtonXColumn bcx =
        dataGridViewShowCourse.Columns["Volunteers"] as DataGridViewButtonColumn;// Like I did nothing
        bcx.UseColumnTextForButtonValue = true;
        bcx.Text = "ADD";
        bcx.Name = "MyButton";
    }

错误显示：Object reference not set to an instance of an object.

我知道用按钮添加新列但我不想这样做，我需要将按钮添加到现有列。使用下面的按钮添加新列的代码

        DataGridViewButtonColumn col = new DataGridViewButtonColumn();
        col.UseColumnTextForButtonValue = true;
        col.Text = "ADD";
        col.Name = "MyButton";
        dataGridViewShowCourse.Columns.Add(col);

由于

Answer 1

您可以使用正确的设置在设置数据源之前添加新的按钮列：

public void showCourse()
{
    SqlCommand com = new SqlCommand("SELECT [Course_ID],[Course_Name],[Course_Type],[Course_Hours],[Course_Duration],[Course_Place],[Trainer_ID],[Volunteers] FROM [VolunteersAffairs].[dbo].[Course_Info]", con);
    SqlDataAdapter da = new SqlDataAdapter();
    DataSet dats = new DataSet();
    da.SelectCommand = com;
    da.Fill(dats, "Course_Info");

    if(dataGridViewShowCourse.Columns["MyButton"] == null){
      var col = new DataGridViewButtonColumn();
      col.UseColumnTextForButtonValue = true;
      col.Text = "ADD";
      col.Name = "MyButton";
      col.DataPropertyName = "Volunteers"; //<-- this is very important
      dataGridViewShowCourse.Columns.Add(col);
    }
    dataGridViewShowCourse.DataSource = dats.Tables["Course_Info"];
}

但我建议您从Volunteers删除SELECT并自行添加新按钮列。

将列设置为最后一个：

col.DisplayIndex =  dataGridViewShowCourse.Columns.Cast<DataGridViewColumn>()
                                          .Count(col=>col.Visible) - 1;