Using the CompareValidator control to compare user input date with today's date

问题

hey..i would like to compare the current date with the date entered by user..however, i'm encountering errors so far..

i tried something like this:

<asp:TextBox id="txtDate1" runat="server" />    
<asp:CompareValidator runat="server" ErrorMessage="The date must be greater than today"
    ControlToValidate="txtDate1" type="date" 
    ValuetoCompare="DateTime.Today.ToShortDateString()" />

and i got an error stating that the value of DateTime.Today.ToShortDateString() of the ValueToCompare property of "" cannot be converted to type 'date' i also tried ValueToCompare="DateTime.Now.Date()" and i got the same error message.

please help me and i greatly appreciate it.

回答1:

You're just using the ValueToCompare property as a literal string. You need to use ASP tags in it if you want to execute code to get a dynamic value. Try this:

<asp:comparevalidator runat="server" 
  errormessage="The date must be greater than today"
  controltovalidate="txtDate1" type="date" 
  valuetocompare="<%# DateTime.Today.ToShortDateString() %>" />

Then in your Page_Load method, call Page.DataBind().

This will execute the databinder code when the page is loaded, and put the value in between the quotes.

回答2:

    <asp:CompareValidator ID="CompareValidator3" runat="server" 
                        ControlToValidate="TextBox1" ErrorMessage="Date should be on or after today" 
                        Operator="GreaterThanEqual" Type="Date">
</asp:CompareValidator>

In the page load event set the validator's value to compare as

CompareValidator3.ValueToCompare = DateTime.Now.ToShortDateString();

回答3:

We can set the ValueToCompare in code behind

        if (!Page.IsPostBack)
        {
           string currentDate = DateTime.Today.ToShortDateString();
           Comparevalidator1.ValueToCompare = currentDate;
        }

for the compare validator:

    <asp:CompareValidator ID="Comparevalidator1" runat="server" ErrorMessage="The date must be greater than today"
    Operator="GreaterThan" ControlToValidate="txtDate1" Type="date" Display="Dynamic" />

Why not use Page.DataBind?

Consider the following scenario. I need to display the gridview only on the click of the Action button. The datasource is defined declaratively. But, if I use Page.DataBind() it will show the grid even on the page load.

 <form id="form1" runat="server">
 <asp:TextBox ID="txtDate1" CssClass="firstBox" runat="server" Text=""></asp:TextBox>
 <asp:CompareValidator ID="Comparevalidator1" runat="server" ErrorMessage="The date must be greater than today"
    Operator="GreaterThan" ControlToValidate="txtDate1" Type="date" Display="Dynamic" />
 <asp:Button ID="btnAction" class="submitButton" runat="server" Text="Action" OnClick="btnAction_Click" />
 <asp:Button ID="btnDummy" class="submitButton" runat="server" Text="Dummy" OnClick="btnDummy_Click" />
 <br />
 <br />

 <asp:GridView ID="GridView1" runat="server" DataSource="<%# EmployeesResult %>">
 </asp:GridView>
 </form>

Code behind

public partial class ThirdTest : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        //Page.DataBind();

        if (!Page.IsPostBack)
        {
           string currentDate = DateTime.Today.ToShortDateString();
           txtDate1.Text = currentDate;
           Comparevalidator1.ValueToCompare = currentDate;
        }
    }

    protected void btnAction_Click(object sender, EventArgs e)
    {
        GridView1.DataBind();
        string value = GridView1.DataSource.ToString();
    }

    protected void btnDummy_Click(object sender, EventArgs e)
    {

    }

    //Propertry
    public List<Employee> EmployeesResult
    {
        get
        {
            List<Employee> employees = new List<Employee>();
            employees.Add(new Employee { EmpID = 1, EmpName = "Emp1" });
            employees.Add(new Employee { EmpID = 2, EmpName = "Emp2" });
            return employees;
        }
    }
  }

回答4:

Try this.

<asp:RequiredFieldValidator ID="RequiredFieldValidator3" runat="server" ErrorMessage="Date is required" ControlToValidate="txtmDate"></asp:RequiredFieldValidator>

<asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server" ErrorMessage="Date is not valid (MM.DD.YYYY)" ControlToValidate="txtDate" ValidationExpression="(0[1-9]|1[012])[- /.](0[1-9]|[12][0-9]|3[01])[- /.](19|20)\d\d" ></asp:RegularExpressionValidator>

The way user input the date (date format) is also Important. In here, I have used MM.DD.YYYY date format.

<asp:CompareValidator ID="CompareValidatorGreaterThanToday" runat="server" ErrorMessage="The date must be greater than today" ControlToValidate="txtDate" Type="date" Operator="GreaterThan" ValueToCompare="<%# DateTime.Today.ToShortDateString() %>" ></asp:CompareValidator>

Then in your Page_Load method (*.aspx.cs), call Page.DataBind().

Example:

protected void Page_Load(object sender, EventArgs e)
{            
   Page.DataBind();
}

回答5:

Try the below written :

<asp:CompareValidator runat="server" ErrorMessage="The date must be greater than today"
ControlToValidate="txtDate1" type="DateTime" 
ValuetoCompare='<%# DateTime.Now.ToString("d") '%> />

来源：https://stackoverflow.com/questions/2264215/using-the-comparevalidator-control-to-compare-user-input-date-with-todays-date

标签

ASP.NET

.net

validation

comparevalidator