dbnull

What should I use to compare DBNull ? Using DBNull.Value or ToString().IsNullOrEmpty()

由 泪湿孤枕 提交于 2019-11-28 02:29:44
问题 I can check for a DBnull on a data row using any of the methods. Either by using if(dr[0][0]==DBNull.Value) //do somethin or by doing if(dr[0][0].ToString().IsNullOrEmpty()) //do something In Both Cases I will be getting same result. But Which one is conecptually right approach. Which was will use less resources 回答1: The first way is somewhat correct. However, more accepted way is: if ( dr[0][0] is DBNull ) And the second way is definitely incorrect. If you use the second way, you will get

DBNull in non-empty cell when reading Excel file through OleDB

由 青春壹個敷衍的年華 提交于 2019-11-28 02:00:58
I use OleDB to read an Excel file. One of the columns has a "Common" format and contains both strings with letters and values consisting of numbers only. String values are retrieved without problem, but pure numerical values are retrieved as DBNull . How to solve? I use the following connection string to open Excel 2003 file (xls): "Provider=Microsoft.Jet.OLEDB.4.0; Data Source=C:\\file.xls; Extended Properties=\"Excel 8.0;HDR=Yes;IMEX=1\"" I found some documentation on Microsoft's website that applies to your scenario. They recommend converting all the numerics to strings. http://support

C# ADO.NET: nulls and DbNull — is there more efficient syntax?

由 血红的双手。 提交于 2019-11-27 11:53:08
问题 I've got a DateTime? that I'm trying to insert into a field using a DbParameter . I'm creating the parameter like so: DbParameter datePrm = updateStmt.CreateParameter(); datePrm.ParameterName = "@change_date"; And then I want to put the value of the DateTime? into the dataPrm.Value while accounting for null s. I thought initially I'd be clever: datePrm.Value = nullableDate ?? DBNull.Value; but that fails with the error Operator '??' cannot be applied to operands of type 'System.DateTime?' and

DBNull if statement

由 徘徊边缘 提交于 2019-11-27 09:00:06
I'm trying to execute a stored procedure and then use an if statement to check for null values and I'm coming up short. I'm a VB guy so please bear with me if I'm making a schoolboy syntax error. objConn = new SqlConnection(strConnection); objConn.Open(); objCmd = new SqlCommand(strSQL, objConn); rsData = objCmd.ExecuteReader(); rsData.Read(); if (!(rsData["usr.ursrdaystime"].Equals(System.DBNull.Value))) { strLevel = rsData["usr.ursrdaystime"].ToString(); } Would this allow me to check whether the SQL connection is returning just a value and if so then populating my string? I'm used to being

ExecuteScalar returns null or DBNull (development or production server)

由 走远了吗. 提交于 2019-11-27 05:59:35
问题 I'm trying to add a column to an existing DataRow in C#. Afterwards the column will be filled with a single value from my database. DataRow dr already exists and column "COLNAME" also exists. comTBP is my SqlCommand . dr["COLNAME"] = Convert.ToInt32(comTBP.ExecuteScalar()); This all works fine if there is a value in my database and ExecuteScalar() can get that value. If I test this code on my development server (local) it also works if ExecuteScalar() return null or DBNull and the value of my

Dealing with System.DBNull in PowerShell

由 扶醉桌前 提交于 2019-11-27 05:59:17
问题 EDIT: As of PowerShell 7 Preview 2, -not [System.DBNull]::Value evaluates to $true , thanks to Joel Sallow via pull request 9794 Spending more time pulling SQL data in PowerShell. Running into issues with [System.DBNull]::Value and how PowerShell behaves with this during comparisons. Here's an example of the behavior I see, along with workarounds #DBNull values don't evaluate like Null... if([System.DBNull]::Value){"I would not expect this to display"} # The text displays. if([string][System

Handle DBNull in C#

由 有些话、适合烂在心里 提交于 2019-11-27 03:38:51
Is there a better/cleaner way to do this? int stockvalue = 0; if (!Convert.IsDBNull(reader["StockValue"])) stockvalue = (int)reader["StockValue"]; The shortest (IMHO) is: int stockvalue = (reader["StockValue"] as int?) ?? 0; Explanation: If reader["StockValue"] is of type int , the value will be returned, and the "??" operator will return the result If reader["StockValue"] is NOT of type int (e.g. DBNull), null will be returned, and the "??" operator will return the value 0 (zero). Chris Marisic The way I handle this is int? stockvalue = reader["StockValue"] as int?; Very simple, clean and one

SQLite equivalent to ISNULL(), NVL(), IFNULL() or COALESCE()

由 随声附和 提交于 2019-11-27 03:36:57
I'd like to avoid having many checks like the following in my code: myObj.someStringField = rdr.IsDBNull(someOrdinal) ? string.Empty : rdr.GetString(someOrdinal); I figured I could just have my query take care of the nulls by doing something like this: SELECT myField1, [isnull](myField1, '') FROM myTable1 WHERE myField1 = someCondition I'm using SQLite though and it doesn't seem to recognize the isnull function. I've also tried some equivalent ones recognized in other databases ( NVL() , IFNULL() and COALESCE() ), but SQLite doesn't seem to recognize any of them. Does anyone have any

Why is this code invalid in C#?

由 亡梦爱人 提交于 2019-11-26 22:12:44
The following code will not compile: string foo = "bar"; Object o = foo == null ? DBNull.Value : foo; I get: Error 1 Type of conditional expression cannot be determined because there is no implicit conversion between 'System.DBNull' and 'string' To fix this, I must do something like this: string foo = "bar"; Object o = foo == null ? DBNull.Value : (Object)foo; This cast seems pointless as this is certainly legal: string foo = "bar"; Object o = foo == null ? "gork" : foo; It seems to me that when the ternary branches are of different types, the compiler will not autobox the values to the type

mysqli prepared statements, insert NULL using bind params

由 拟墨画扇 提交于 2019-11-26 22:05:49
问题 Does anyone know if it is possible to insert NULL into a column with MYSQLI bind_param. I have a situation where sometimes I want to set a column to null in bind_param. Like so... $column2 = "NULL"; $insert_data->bind_param('ss', $column1,$column2); Obviously, this just writes NULL to the column as a string. I've tried null and \0 but they don't work. I would like to know if there is some value I can make $column2 equal that will cause it to submit and actual null value instead. Otherwise, I
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