LINQ查询不断抛出"无法建立System.Object类型的恒定值....",为什么呢? [英] Linq Query keeps throwing "Unable to create a constant value of type System.Object....", Why?
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问题描述
以下是代码示例:
private void loadCustomer(int custIdToQuery)
{
var dbContext = new SampleDB();
try
{
var customerContext = from t in dbContext.tblCustomers // keeps throwing:
where t.CustID.Equals(custIdToQuery) // Unable to create a constant value of type 'System.Object'.
select new // Only primitive types ('such as Int32, String, and Guid')
{ // are supported in this context.
branchId = t.CustomerBranchID, //
branchName = t.BranchName //
}; //
if (customerContext.ToList().Count() < 1) //Already Tried customerContext.Any()
{
lstbCustomers.DataSource = customerContext;
lstbCustomers.DisplayMember = "branchName";
lstbCustomers.ValueMember = "branchId";
}
else
{
lstbCustomers.Items.Add("There are no branches defined for the selected customer.");
lstbCustomers.Refresh();
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
finally
{
dbContext.Dispose();
}
}
我无法明白我做错了。我不断收到无法创建类型'System.Object的恒定值,只有原始类型('如的Int32,字符串和GUID')在这方面的支持。
推荐答案
使用的==而不是等于:
Use == instead of Equals:
where t.CustID == custIdToQuery
如果该类型是不正确的,你可能会发现,这并未T编译。
If the types are incorrect you may find that this doesn't compile.
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