我在以下事件中绑定gridview:(subjectdropdown_SelectedIndexChanged)我将以下事件中的gridview作为参数发送到另一个方法:Button1_click事件。
protected void subjectdropdown_SelectedIndexChanged(object sender, EventArgs e)
{
DataTable getmarkfdb = inter.getmarksfromdatabaseothers(comp);
if (getmarkfdb.Rows.Count > 0)
{
TemplateField lable1 = new TemplateField();
lable1.ShowHeader = true;
lable1.HeaderText = "AdmissionNumber";
lable1.ItemTemplate = new gridviewtemplate(DataControlRowType.DataRow, "AdmissionNumber", "AdmissionNumber", "Label");
studmarkgrid.Columns.Add(lable1);
TemplateField label2 = new TemplateField();
label2.ShowHeader = true;
label2.HeaderText = "RollNumber";
label2.ItemTemplate = new gridviewtemplate(DataControlRowType.DataRow, "RollNumber", "RollNumber", "Label");
studmarkgrid.Columns.Add(label2);
TemplateField label3 = new TemplateField();
label3.ShowHeader = true;
label3.HeaderText = "Name";
label3.ItemTemplate = new gridviewtemplate(DataControlRowType.DataRow, "Name", "Name", "Label");
studmarkgrid.Columns.Add(label3);
TemplateField extmep = new TemplateField();
extmep.ShowHeader = true;
extmep.HeaderText = "ExternalMark";
extmep.ItemTemplate = new gridviewtemplate(DataControlRowType.DataRow, "ExternalMark", "ExternalMark", "TextBox");
studmarkgrid.Columns.Add(extmep);
studmarkgrid.DataSource = getmarkfdb;
studmarkgrid.DataBind();
}
}
在gridview的TextBoxTemplate列中,我填写了Mark for student,在下面的事件中,我将gridview发送到insertstumark方法,用于从gridview读取数据并保存到数据库中。但是在insertstumark方法中,gridview行数据为null。
protected void Button1_Click(object sender, EventArgs e)
{
comp.ACADAMICYEAR = acyeardropdown.SelectedItem.Text;
comp.MEDIUM = mediumdropdown.SelectedItem.Text;
string clas = classdropdown.SelectedItem.Text;
string[] cs = clas.Split('-');
comp.CLASSNAME = cs[0].ToString();
comp.SECTIONNAME =Convert.ToChar(cs[1].Trim().ToString());
comp.EXAMNAMES = examnamedropdown.SelectedItem.Text;
comp.SUBJECTID = subjectdropdown.SelectedValue.ToString();
// studmarkgrid.DataBind();
// System.Web.UI.WebControls.GridView grid = studmarkgrid;
// System.Web.UI.WebControls.GridView grid = ViewState["stdmarkgrid"] as System.Web.UI.WebControls.GridView;
DataTable studtable = null;
// System.Web.UI.WebControls.GridView grid = (System.Web.UI.WebControls.GridView)ViewState["stdmarkgrid"];
bool studm = inter.inserstumark(comp,stumarkgrid);
}
问题是什么。我试图将gridview存储在viewstate中。但在下面的行中它通过错误。如何解决这个问题呢?
System.Web.UI.WebControls.GridView grid = ViewState["stdmarkgrid"] as System.Web.UI.WebControls.GridView;
很多时候,如果在页面生命周期中数据绑定到GridView太晚,则会渲染GridView,并且数据会被遗忘,因此在下一个PostBack中,您将无法访问GridView的底层数据源。
这看起来像是在这里发生的事情。只需将getmarksfromdatabaseothers
的结果保存到ViewState,以便您可以根据需要再次访问它。