Question

我正在开发一个继承自DataBoundControl的控件。数据绑定有效，但由于某种原因，在回发时清除了视图状态？我已经尝试过各种各样的解决方案，比如让它实现ViewStateModeById属性，但没有任何效果。有人能指出我正确的方向吗？

public class Test : DataBoundControl, INamingContainer
{
    protected override void OnLoad(EventArgs e)
    {
        base.OnLoad(e);
        if (this.Visible && !_isDataBound)
        {
            // If the developer wants to show it on click or something then they will have to call DataBind() themselves
            // If this control has just been put on a page and there is no code behind then we need to make it get data and call DataBind
            FlagForDataBinding();
            DataBind();
        }
    }

    protected override void OnPreRender(EventArgs e)
    {
        if (!_isDataBound || RequiresDataBinding)
        {
            DataBind();
        }
        base.OnPreRender(e);
    }

    private bool _isDataBound = false;
    public override object DataSource
    {
        get { return Enumerable.Range(0, 10); }
        set
        {}
    }

    public virtual void FlagForDataBinding()
    {
        this.DataSource = null;
        if (_isDataBound)
        {
            _isDataBound = false;
        }
        else
            this.RequiresDataBinding = true;
    }

    protected override void PerformSelect()
    {
        if (!IsBoundUsingDataSourceID)
        {
            // If using .DataSource then databinding starts here
            // (Because the the data has alredy been retrieved when doing .DataSource = )
            OnDataBinding(EventArgs.Empty);
        }

        GetData().Select(CreateDataSourceSelectArguments(), OnDataReady);

        RequiresDataBinding = false;
        MarkAsDataBound();

        OnDataBound(EventArgs.Empty);
    }

    protected virtual void OnDataReady(IEnumerable data)
    {
        if (IsBoundUsingDataSourceID)
        {
            // If using .DataSourceId then databinding starts here
            OnDataBinding(EventArgs.Empty);
        }
        PerformDataBinding(data);
    }

    protected override void PerformDataBinding(IEnumerable data)
    {
        this.Controls.Clear();
        if (data != null)
        {
            OutputItems((IEnumerable<int>)data);
        }
        base.PerformDataBinding(data);
    }

    public override void DataBind()
    {
        this.EnsureChildControls();
        if (!_isDataBound || RequiresDataBinding)
        {
            base.OnDataBinding(EventArgs.Empty);
            base.DataBind();
            _isDataBound = true;
        }
    }

    protected virtual void OutputItems(IEnumerable<int> items)
    {
        this.Controls.Clear();
        foreach (var item in items)
        {
            var lnk = new LinkButton {Text = item.ToString(), CommandArgument = item.ToString()};
            lnk.Click += lnk_Click;
            this.Controls.Add(lnk);
        }
        this.Controls.Add(new Literal{Text = "Total: " + Total});
    }

    void lnk_Click(object sender, EventArgs e)
    {
        int toAdd = int.Parse((sender as LinkButton).CommandArgument);
        Total += toAdd;
        FlagForDataBinding();
    }

    public int Total {
        get { return (int?) ViewState["Total"] ?? 0; }
        set { ViewState["Total"] = value; }
    }

}

Answer 1

尝试在DataBoundControl上设置EnableViewState =“true”和ViewStateMode =“Enabled”。

此外，还要确保页面的EnableViewState =“true”。

https://msdn.microsoft.com/en-us/library/system.web.ui.control.enableviewstate(v=vs.110).aspx

在DataBoundControl中回发时清除ViewState

1 个答案: