从ASP.NET GridView动态添加和删除行

Question

我已经将以下来自网络“ codeproject ”的代码用于“从ASP.NET GridView动态添加和删除行”，它使用了2个代码“ AddNewRow”，“ SetPreviouseData”。 我在理解“ SetPreviouseData”的代码时遇到问题，当定义时，似乎所有操作都将使用“ AddNewRow”代码完成

grvStudentDetails.DataSource = dtCurrentTable;
grvStudentDetails.DataBind();

实际上，我之前不知道什么时候定义了数据源，但是“ SetPreviouseData”代码的用途是什么。

    private void AddNewRow()
{
    int rowIndex = 0;

    if (ViewState["CurrentTable"] != null)
    {
        DataTable dtCurrentTable = (DataTable)ViewState["CurrentTable"];
        DataRow drCurrentRow = null;
        if (dtCurrentTable.Rows.Count > 0)
        {
            for (int i = 1; i <= dtCurrentTable.Rows.Count; i++)
            {
                TextBox TextBoxName = (TextBox)grvStudentDetails.Rows[rowIndex].Cells[1].FindControl("txtName");
                TextBox TextBoxAge = (TextBox)grvStudentDetails.Rows[rowIndex].Cells[2].FindControl("txtAge");
                TextBox TextBoxAddress = 
                  (TextBox)grvStudentDetails.Rows[rowIndex].Cells[3].FindControl("txtAddress");
                RadioButtonList RBLGender = 
                  (RadioButtonList)grvStudentDetails.Rows[rowIndex].Cells[4].FindControl("RBLGender");
                DropDownList DrpQualification = 
                  (DropDownList)grvStudentDetails.Rows[rowIndex].Cells[5].FindControl("drpQualification");
                drCurrentRow = dtCurrentTable.NewRow();
                drCurrentRow["RowNumber"] = i + 1;

                dtCurrentTable.Rows[i - 1]["Col1"] = TextBoxName.Text;
                dtCurrentTable.Rows[i - 1]["Col2"] = TextBoxAge.Text;
                dtCurrentTable.Rows[i - 1]["Col3"] = TextBoxAddress.Text;
                dtCurrentTable.Rows[i - 1]["Col4"] = RBLGender.SelectedValue;
                dtCurrentTable.Rows[i - 1]["Col5"] = DrpQualification.SelectedValue;
                rowIndex++;
            }
            dtCurrentTable.Rows.Add(drCurrentRow);
            ViewState["CurrentTable"] = dtCurrentTable;

            grvStudentDetails.DataSource = dtCurrentTable;
            grvStudentDetails.DataBind();
        }
    }
    else
    {
        Response.Write("ViewState is null");
    }
    SetPreviousData();
}


    private void SetPreviousData()
     {
    int rowIndex = 0;
    if (ViewState["CurrentTable"] != null)
    {
        DataTable dt = (DataTable)ViewState["CurrentTable"];
        if (dt.Rows.Count > 0)
        {
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                TextBox TextBoxName =  (TextBox)grvStudentDetails.Rows[rowIndex].Cells[1].FindControl("txtName");
                TextBox TextBoxAge = (TextBox)grvStudentDetails.Rows[rowIndex].Cells[2].FindControl("txtAge");
                TextBox TextBoxAddress = (TextBox)grvStudentDetails.Rows[rowIndex].Cells[3].FindControl("txtAddress");
                RadioButtonList RBLGender = (RadioButtonList)grvStudentDetails.Rows[rowIndex].Cells[4].FindControl("RBLGender");
                DropDownList DrpQualification = (DropDownList)grvStudentDetails.Rows[rowIndex].Cells[5].FindControl("drpQualification");

                TextBoxName.Text = dt.Rows[i]["Col1"].ToString();
                TextBoxAge.Text = dt.Rows[i]["Col2"].ToString();
                TextBoxAddress.Text = dt.Rows[i]["Col3"].ToString();
                RBLGender.SelectedValue = dt.Rows[i]["Col4"].ToString();
                DrpQualification.SelectedValue = dt.Rows[i]["Col5"].ToString();
                rowIndex++;
            }
        }
    }
    }

Answer 1

从代码中， AddNewRow已经清除，而SetPreviouseData似乎用于将最后一个数据显示到组件中（TextBox，RadioButtonList，DropDownList）。

    // Get the reference to the objects (TextBoxes, RadioButtonList, DropDownList)
    TextBox TextBoxName =  (TextBox)grvStudentDetails.Rows[rowIndex].Cells[1].FindControl("txtName");
    TextBox TextBoxAge = (TextBox)grvStudentDetails.Rows[rowIndex].Cells[2].FindControl("txtAge");
    TextBox TextBoxAddress = (TextBox)grvStudentDetails.Rows[rowIndex].Cells[3].FindControl("txtAddress");
    RadioButtonList RBLGender = (RadioButtonList)grvStudentDetails.Rows[rowIndex].Cells[4].FindControl("RBLGender");
    DropDownList DrpQualification = (DropDownList)grvStudentDetails.Rows[rowIndex].Cells[5].FindControl("drpQualification");

    // Set the value of the objects to the last on the DataTable
    TextBoxName.Text = dt.Rows[i]["Col1"].ToString();
    TextBoxAge.Text = dt.Rows[i]["Col2"].ToString();
    TextBoxAddress.Text = dt.Rows[i]["Col3"].ToString();
    RBLGender.SelectedValue = dt.Rows[i]["Col4"].ToString();
    DrpQualification.SelectedValue = dt.Rows[i]["Col5"].ToString();