dbnull

New to Linq, so apologies if this is basic. This query is throwing up the error {"Cannot cast DBNull.Value to type 'System.Int64'. Please use a nullable type."} when I enumerate the results. private void AddLevels(long rootid) { var results = from row in data.AsEnumerable() where row.Field<long>("ParentID") == rootid select row; foreach (DataRow row in results) { //do stuff } } The column ParentID does accept nulls - do I need to handle these separately? EDIT2: Actual solution below that still uses Linq. EDIT: I solved this by scrapping Linq and just using a DataTable.Select statement instead.

How can I add a null value in a parameter varbinary datatype? When I execute the following code: using (SqlConnection myDatabaseConnection1 = new SqlConnection(myConnectionString.ConnectionString)) { using (SqlCommand mySqlCommand = new SqlCommand("INSERT INTO Employee(EmpName, Image) Values(@EmpName, @Image)", myDatabaseConnection1)) { mySqlCommand.Parameters.AddWithValue("@EmpName", textBoxEmpName.Text); mySqlCommand.Parameters.AddWithValue("@Image", DBNull.Value); myDatabaseConnection1.Open(); mySqlCommand.ExecuteNonQuery(); } } I get the following System.Data.SqlClient.SqlException :

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 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 true in two cases: Your value is DBNull Your value is an empty string Conceptually the comparison to DBNull

i am receiving this problem Conversion from type 'DBNull' to type 'String' is not valid. Line 501: hfSupEmail.Value = dt.Rows(0)("SupEmail") i am very new to this, i am not really sure what is the exact problem could someone guide me? Many thanks The quick and dirty fix: hfSupEmail.Value = dt.Rows(0)("SupEmail").ToString() This works very well when your eventual target and the source data are already strings. This is because any extra .ToString() call for something that's already a string will generally be optimized by the jitter into a no-op, and if it's NULL then the resulting DBNull.Value

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 'System.DBNull' So I guess that only works if the second argument is a non-nullable version of the

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 new column is 0. But the problem appears if I deploy my code to the production server. If I do

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.DBNull]::Value){"This won't display, but is not intuitive"} # The text does not display. #DBNull does