C# 使用 DateTime 列设置 LinqDataSource Where 子句
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Setting the LinqDataSource Where Clause using DateTime Column
提问by BrianG
In C#.net, I have the following DataSource setup that I am trying to dynamically assign a WHERE clause to in the code behind...
在 C#.net 中，我有以下数据源设置，我试图在后面的代码中动态分配一个 WHERE 子句......
<asp:LinqDataSource ID="LinqDataSource1" runat="server"
ContextTypeName="MyNameSpace.DataClasses1DataContext"
TableName="MyTableWithADateTimeColumn" >
</asp:LinqDataSource>
The code behind looks something like this...
后面的代码看起来像这样......
LinqDataSource1.Where = "MyDateColumn == DateTime(" + DateTime.Now + ")";
This gives me an error of ')' or ',' expected. I've also tried casting it inside quotation marks, as well, as without casting it as DateTime and with quotation marks...
这给了我一个错误')' or ',' expected。我也试过将它转换为引号，因为没有将它转换为 DateTime 并且使用引号......
LinqDataSource1.Where = @"MyDateColumn == """ + DateTime.Now + @""" ";
This gives me Operator '==' incompatible with operand types 'DateTime' and 'String'. I've tried several other ways, but I am obviously missing something here.
这给了我Operator '==' incompatible with operand types 'DateTime' and 'String'。我尝试了其他几种方法，但显然我在这里遗漏了一些东西。
Similar code is working fine for strings.
类似的代码适用于字符串。
采纳答案by bytebender
is it this? What about this then...
是这个吗？那这怎么办……
LinqDataSource1.Where = "MyDateColumn == DateTime.Parse(" + DateTime.Now + ")";
//can't create a date from string in constructor use .Parse()...
回答by Reed Copsey
I believe you need to include double quotes around the string being converted to a DateTime.
我相信您需要在转换为 DateTime 的字符串周围包含双引号。
LinqDataSource1.Where = "MyDateColumn == DateTime(\"" + DateTime.Now.ToString() + "\")";
回答by BrianG
So the final solution as suggested by J.13.L looked like this...
所以 J.13.L 建议的最终解决方案看起来像这样......
LinqDataSource1.Where = @"MyDateColumn == DateTime.Parse(""" + MyDateTime + @""") ";
But since I didn't want to match on the time part of the date it really looked more like this...
但是由于我不想匹配日期的时间部分，所以它看起来更像是这样......
LinqDataSource1.Where = @"MyDateColumn >= DateTime.Parse(""" + MyDateTime + @""") AND MyDateColumn < DateTime.Parse(""" + MyDateTime.AddDays(1) + @""")";
回答by BrianG
Another programmatically way:
另一种编程方式：
dataSource.WherePredicateParameters.Clear();
OrExpressionParameter expression = new OrExpressionParameter();
expression.Parameters.Add("Birthday", DbType.DateTime, Convert.ToDateTime(txtBirthday.Text).ToString());
dataSource.WherePredicateParameters.Add(expression);
回答by Venugopal
LinqDataSource1.Where = "MyDateColumn == Convert.ToDateTime(\"" + DateTime.Now + "\")";
LinqDataSource1.Where = "MyDateColumn == Convert.ToDateTime(\"" + DateTime.Now + "\")";
回答by Sanjay Gupta
It's simple and straight forward:
这很简单直接：
Look in the page source of "asp:LinqDataSource" and add that clause in the "where" section.
查看“asp:LinqDataSource”的页面源代码并在“where”部分添加该子句。
Adding this through the wizard with a NULL parameter fails.
通过向导添加 NULL 参数失败。
Here is an example:
下面是一个例子：
<asp:LinqDataSource ID="LinqDataSource1" runat="server" ContextTypeName="MyDataContext"
EntityTypeName="" GroupBy="MyItem" Select="new (key as Item1, Count() as TotalQuantity)"
TableName="MyTable"
Where="Country == @Country && DateProcessed == NULL">
<WhereParameters>
<asp:ControlParameter ControlID="ddlCountry" DefaultValue="US"
Name="Country" PropertyName="SelectedValue" Type="String" />
</WhereParameters>
</asp:LinqDataSource>
