ado.net

问题 I'm trying out the in-memory shared cache feature of SQLite 3.7.13, via the ADO.NET provider. The following connect string works, but yields a non-shared-cache db: Data Source=:memory: When I try any of these: Data Source=:memory:?cache=shared Data Source=file::memory:?cache=shared Data Source=file:x?mode=memory&cache=shared I get the following ArgumentException when opening a connection: Invalid ConnectionString format for parameter "Data Source" What should the connect string look like for

问题 I'm trying out the in-memory shared cache feature of SQLite 3.7.13, via the ADO.NET provider. The following connect string works, but yields a non-shared-cache db: Data Source=:memory: When I try any of these: Data Source=:memory:?cache=shared Data Source=file::memory:?cache=shared Data Source=file:x?mode=memory&cache=shared I get the following ArgumentException when opening a connection: Invalid ConnectionString format for parameter "Data Source" What should the connect string look like for

问题 This question already has answers here : How to select distinct rows in a datatable and store into an array (18 answers) Closed 5 years ago . I have a table with 10 columns and I want to get all values of each row but only of distinct IDs. I have this so far: DataTable Distinct = view.ToTable(true, "ID"); But this creates a DataTable that only contains the ID column. I want a DataTable with distinct ID's but containing all column values(there can be duplicates for the other columns.) Is there

问题 I am converting ado.net code to use EF. In my ado.net code i set dataReader.FetchSize = command.RowSize * 1000 and that dramatically improves performance over the default fetch size . When I convert my code to EF, the performance is on par to ado.net code where I didn't specify fetch size, i.e. it's very slow over large records. Any way I could specify fetch size for retrieving records in EF? 回答1: You can set ODP.NET FetchSize in the Registry or the .NET config files when using Entity

问题 Consider the sample code below. If the connection to the database is suddenly broken when on STEP 2 (i.e. 2nd command), then even if we try to rollback the transaction it will not rollback since there is no connection to the database server. In such a case, what happens to the transaction object on the database server side? Will it remain in a waiting mode? I have had this situation come up when I tried to run a long transaction in ADO.Net by connecting to database servers through a VPN

问题 Consider the sample code below. If the connection to the database is suddenly broken when on STEP 2 (i.e. 2nd command), then even if we try to rollback the transaction it will not rollback since there is no connection to the database server. In such a case, what happens to the transaction object on the database server side? Will it remain in a waiting mode? I have had this situation come up when I tried to run a long transaction in ADO.Net by connecting to database servers through a VPN

问题 I am using EntityFramework as my Data Access Layer in a Visual Studio C# project. I have added a new entity model and built right away without adding or doing anything to test its functionality. Unfortunately, the build failed with many errors like: CS0426 The type name 'Data' does not exist in the type 'System' CS0138 A 'using namespace' directive can only be applied to namespaces; 'System' is a type not a namespace. Consider a 'using static' directive instead CS0246 The type or namespace

问题 I am using EntityFramework as my Data Access Layer in a Visual Studio C# project. I have added a new entity model and built right away without adding or doing anything to test its functionality. Unfortunately, the build failed with many errors like: CS0426 The type name 'Data' does not exist in the type 'System' CS0138 A 'using namespace' directive can only be applied to namespaces; 'System' is a type not a namespace. Consider a 'using static' directive instead CS0246 The type or namespace

问题 My database connections from my web servers work fine normally, but when a write heavy windows service I have triggers, I will randomly get "A network-related or instance-specific error occurred while establishing a connection to SQL Server. Error 40." from my webservers. I have tried turning connection pooling off for my web servers since they share the same connection string as the windows service, but I am at a loss as to what is still causing this. My SqlConnection objects are all wrapped

问题 My database connections from my web servers work fine normally, but when a write heavy windows service I have triggers, I will randomly get "A network-related or instance-specific error occurred while establishing a connection to SQL Server. Error 40." from my webservers. I have tried turning connection pooling off for my web servers since they share the same connection string as the windows service, but I am at a loss as to what is still causing this. My SqlConnection objects are all wrapped