“Parameter ?_1 has no default value” error when ExecuteReader

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情深已故
情深已故 2021-01-26 04:10

Having problem with the code below in a web service. Have searched for a solution but nothing that I have seen seems different to what I am doing below.

NB: The

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  • 2021-01-26 04:22

    The question in fact had a wrong assumption and that was that there was an error in the code.

    The syntax of the SQL query was correct and the parameter was being inserted correctly. However the test data contained errors and therefore no result was being returned by a correctly formatted query.

    Thanks all for input.

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  • 2021-01-26 04:26

    What you have looks correct with the "?" as the parameter place-holder for the parameters added to the command. You currently have the parameter identified as OleDbType.VarWChar. Is that intended? Are you dealing with unicode data? I suspect not in this case. Try changing to OleDbType.Char which also is represented to handle System.String values.

    You could also make sure you are getting a string by using

    AccountNo.ToString()

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  • 2021-01-26 04:34

    Duplicated of: OleDbCommand parameters order and priority

    The OLE DB .NET Provider does not support named parameters for passing parameters to an SQL statement or a stored procedure called by an OleDbCommand when CommandType is set to Text. In this case, the question mark (?) placeholder must be used. For example:

    // Create SQL with ? for each parameter
    String sql = "SELECT Address FROM Adresses WHERE Country = ? AND City = ?";
    OleDbCommand command = new OleDbCommand(sql , connection);
    
    // Add to command each paramater VALUE by position. 
    // One parameter value for ?
    command.Parameters.Add("My City") ;
    command.Parameters.Add("My Country") ;
    

    http://msdn.microsoft.com/en-us/library/system.data.oledb.oledbcommand.parameters.aspx

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  • 2021-01-26 04:41

    It's a shame that the top two StackOverflow results currently in Google for searches involving

    Parameter ?_ has no default value
    

    both have the questioner coming back in and saying there were flaws in their original question or their test data or whatever (though it's great that questioners check back in).

    The explanation for this error (as encountered in normal situations) is supplied by Marc Gravell here:

    Parameters with a .Value of null are not passed. At all.

    You need to pass DBNull.Value instead to pass a semantic null. For example:

    com.Parameters.Add("@p7", OleDbType.Char, 255).Value =
             ((object)values7[0]) ?? DBNull.Value; (etc)
    
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