我有一个问题困扰了我一整天。
在我的代码中有以下内容:
private int rowCount
{
get { return (int)ViewState["rowCount"]; }
set { ViewState["rowCount"] = value; }
}
和一个按钮事件
protected void addRow_Click(object sender, EventArgs e)
{
rowCount = rowCount + 1;
}
然后在 Page_Load 上我读取该值并相应地创建控件。
我知道按钮事件在 Page_Load 触发后触发，因此直到下一次回发时该值才会更新。真正的噩梦。
完整代码如下:
protected void Page_Load(object sender, EventArgs e)
{
string xmlValue = ""; //To read a value from a database
if (xmlValue.Length > 0)
{
if (!Page.IsPostBack)
{
DataSet ds = XMLToDataSet(xmlValue);
Table dimensionsTable = DataSetToTable(ds);
tablePanel.Controls.Add(dimensionsTable);
DataTable dt = ds.Tables["Dimensions"];
rowCount = dt.Rows.Count;
colCount = dt.Columns.Count;
}
else
{
tablePanel.Controls.Add(DataSetToTable(DefaultDataSet(rowCount, colCount)));
}
}
else
{
if (!Page.IsPostBack)
{
rowCount = 2;
colCount = 4;
}
tablePanel.Controls.Add(DataSetToTable(DefaultDataSet(rowCount, colCount)));
}
}
protected void submit_Click(object sender, EventArgs e)
{
resultsLabel.Text = Server.HtmlEncode(DataSetToStringXML(TableToDataSet((Table)tablePanel.Controls[0])));
}
protected void addColumn_Click(object sender, EventArgs e)
{
colCount = colCount + 1;
}
protected void addRow_Click(object sender, EventArgs e)
{
rowCount = rowCount + 1;
}
public DataSet TableToDataSet(Table table)
{
DataSet ds = new DataSet();
DataTable dt = new DataTable("Dimensions");
ds.Tables.Add(dt);
//Add headers
for (int i = 0; i < table.Rows[0].Cells.Count; i++)
{
DataColumn col = new DataColumn();
TextBox headerTxtBox = (TextBox)table.Rows[0].Cells[i].Controls[0];
col.ColumnName = headerTxtBox.Text;
col.Caption = headerTxtBox.Text;
dt.Columns.Add(col);
}
for (int i = 0; i < table.Rows.Count; i++)
{
DataRow valueRow = dt.NewRow();
for (int x = 0; x < table.Rows[i].Cells.Count; x++)
{
TextBox valueTextBox = (TextBox)table.Rows[i].Cells[x].Controls[0];
valueRow[x] = valueTextBox.Text;
}
dt.Rows.Add(valueRow);
}
return ds;
}
public Table DataSetToTable(DataSet ds)
{
DataTable dt = ds.Tables["Dimensions"];
Table newTable = new Table();
//Add headers
TableRow headerRow = new TableRow();
for (int i = 0; i < dt.Columns.Count; i++)
{
TableCell headerCell = new TableCell();
TextBox headerTxtBox = new TextBox();
headerTxtBox.ID = "HeadersTxtBox" + i.ToString();
headerTxtBox.Font.Bold = true;
headerTxtBox.Text = dt.Columns[i].ColumnName;
headerCell.Controls.Add(headerTxtBox);
headerRow.Cells.Add(headerCell);
}
newTable.Rows.Add(headerRow);
//Add value rows
for (int i = 0; i < dt.Rows.Count; i++)
{
TableRow valueRow = new TableRow();
for (int x = 0; x < dt.Columns.Count; x++)
{
TableCell valueCell = new TableCell();
TextBox valueTxtBox = new TextBox();
valueTxtBox.ID = "ValueTxtBox" + i.ToString() + i + x + x.ToString();
valueTxtBox.Text = dt.Rows[i][x].ToString();
valueCell.Controls.Add(valueTxtBox);
valueRow.Cells.Add(valueCell);
}
newTable.Rows.Add(valueRow);
}
return newTable;
}
public DataSet DefaultDataSet(int rows, int cols)
{
DataSet ds = new DataSet();
DataTable dt = new DataTable("Dimensions");
ds.Tables.Add(dt);
DataColumn nameCol = new DataColumn();
nameCol.Caption = "Name";
nameCol.ColumnName = "Name";
nameCol.DataType = System.Type.GetType("System.String");
dt.Columns.Add(nameCol);
DataColumn widthCol = new DataColumn();
widthCol.Caption = "Width";
widthCol.ColumnName = "Width";
widthCol.DataType = System.Type.GetType("System.String");
dt.Columns.Add(widthCol);
if (cols > 2)
{
DataColumn heightCol = new DataColumn();
heightCol.Caption = "Height";
heightCol.ColumnName = "Height";
heightCol.DataType = System.Type.GetType("System.String");
dt.Columns.Add(heightCol);
}
if (cols > 3)
{
DataColumn depthCol = new DataColumn();
depthCol.Caption = "Depth";
depthCol.ColumnName = "Depth";
depthCol.DataType = System.Type.GetType("System.String");
dt.Columns.Add(depthCol);
}
if (cols > 4)
{
int newColCount = cols - 4;
for (int i = 0; i < newColCount; i++)
{
DataColumn newCol = new DataColumn();
newCol.Caption = "New " + i.ToString();
newCol.ColumnName = "New " + i.ToString();
newCol.DataType = System.Type.GetType("System.String");
dt.Columns.Add(newCol);
}
}
for (int i = 0; i < rows; i++)
{
DataRow newRow = dt.NewRow();
newRow["Name"] = "Name " + i.ToString();
newRow["Width"] = "Width " + i.ToString();
if (cols > 2)
{
newRow["Height"] = "Height " + i.ToString();
}
if (cols > 3)
{
newRow["Depth"] = "Depth " + i.ToString();
}
dt.Rows.Add(newRow);
}
return ds;
}
public DataSet XMLToDataSet(string xml)
{
StringReader sr = new StringReader(xml);
DataSet ds = new DataSet();
ds.ReadXml(sr);
return ds;
}
public string DataSetToStringXML(DataSet ds)
{
XmlDocument _XMLDoc = new XmlDocument();
_XMLDoc.LoadXml(ds.GetXml());
StringWriter sw = new StringWriter();
XmlTextWriter xw = new XmlTextWriter(sw);
XmlDocument xml = _XMLDoc;
xml.WriteTo(xw);
return sw.ToString();
}
private int rowCount
{
get { return (int)ViewState["rowCount"]; }
set { ViewState["rowCount"] = value; }
}
private int colCount
{
get { return (int)ViewState["colCount"]; }
set { ViewState["colCount"] = value; }
}
编辑:这也是我的 .aspx，以防您想在 VS 中试用它。
<asp:Panel ID="tablePanel" runat="server" CssClass="table-panel" />
<asp:Label ID="resultsLabel" runat="server" />
<asp:LinkButton ID="submit" Text="submit" runat="server" onclick="submit_Click" />
<asp:LinkButton ID="addColumn" Text="Add Column" runat="server"
onclick="addColumn_Click" />
<asp:LinkButton ID="addRow" Text="Add Row" runat="server" onclick="addRow_Click" />
提前致谢
马可
最佳答案
正如我在 this other question 中推荐的那样，如果您希望在按钮的 Click 事件之后执行某些页面逻辑，请将该代码放入 Page_PreRender 中。
您可以在这里阅读更多相关信息:ASP.NET page life cycle .
编辑:
在更仔细地检查您的代码后，我发现您添加了东西并创建了新控件，这在 PreRender 事件中不是一个好主意。 相反，将代码放入一个单独的方法中。在 Page_Load 中，检查它是否是回发，如果不是，则进行处理。 在按钮的单击事件中，还添加对该新方法的调用。 (从而处理 IsPostback == true 的情况)
关于c# Counter 需要点击 2 次按钮才能更新，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/2800496/