string must be exactly one character long

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LINQ

i am facing one problem, i don't know why this occurs please help.
when i try to get first result of the linq query, query return null value, while in db, there is record.
when i pass PosCustomerID=00445856363109679106 is working corrent no error. but when i pass PosCustomerID=00445856363109679107 its throw an exception:"string must be exactly one character long"

my code query is:

<pre lang="C#"> POSCustomer updCustomer = (from lC in UpdateCustomerDB.POSCustomers
where lC.POSCustomerID == lBShipToAddress.PosCustomerID
select lC).Single();

i also try this:
1)POSCustomer updCustomer = (from lC in UpdateCustomerDB.POSCustomers
where lC.POSCustomerID == lBShipToAddress.PosCustomerID
select lC).SingleOrDefault();
2)
POSCustomer updCustomer = (from lC in UpdateCustomerDB.POSCustomers
where lC.POSCustomerID == lBShipToAddress.PosCustomerID
select lC).FirstOrDefault();
3)
POSCustomer updCustomer = (from lC in UpdateCustomerDB.POSCustomers
where lC.POSCustomerID == lBShipToAddress.PosCustomerID
select lC).First();


my linq.dbml code generated for that fiels are below:

[global::System.Data.Linq.Mapping.ColumnAttribute(Storage=&amp;quot;_POSCustomerID&amp;quot;, DbType=&amp;quot;VarChar(23) NOT NULL&amp;quot;, CanBeNull=false, IsPrimaryKey=true)]
public string POSCustomerID
{
get
{
return this._POSCustomerID;
}
set
{
if ((this._POSCustomerID != value))
{
this.OnPOSCustomerIDChanging(value);
this.SendPropertyChanging();
this._POSCustomerID = value;
this.SendPropertyChanged(&amp;quot;POSCustomerID&amp;quot;);
this.OnPOSCustomerIDChanged();
}
}
}&lt;/pre&gt;</pre>
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