C# Sqlite InvalidCastException

Question

I was unable to find a answer that helped me so here we go,

I have this function that makes a command for my SQLiteDataAdapter, Now it works all nice in my program that uses FireBird, sadly enough im now working on a mobile framework and it doesnt seem to work here.

public DataTable Get(string tableName, string[] selectColumns, string[] conditionColumns,
                         object[] conditionValues)
    {
        if (conditionColumns.Length != conditionValues.Length)
        {
            throw new Exception("Length of columns and values is different");
        }

        DataTable dt = new DataTable();
        StringBuilder stringB = new StringBuilder();
        try
        {
            stringB.Append("SELECT ");
            if (selectColumns == null)
            {
                stringB.Append("* ");
            }
            else
            {
                for (int i = 0; i < selectColumns.Length; i++)
                {
                    stringB.Append(selectColumns[i]);
                    if (i == selectColumns.Length - 1)
                    {
                        stringB.Append(" ");
                    }
                    else
                    {
                        stringB.Append(", ");
                    }
                }
            }
            stringB.Append("FROM ");
            stringB.Append(tableName + " ");
            stringB.Append("WHERE (");
            for (int i = 0; i < conditionColumns.Length; i++)
            {
                stringB.Append(conditionColumns[i] + " = @" + conditionColumns[i]);
                if (i < (conditionColumns.Length - 1))
                {
                    stringB.Append(" AND ");
                }
                else
                {
                    stringB.Append(")");
                }
            }
            SQLiteDataAdapter da = new SQLiteDataAdapter(stringB.ToString(), connection);

            for (int i = 0; i < conditionColumns.Length; i++)
            {
                da.SelectCommand.Parameters.Add("@" + conditionColumns[i], (DbType)conditionValues[i]);
            }
            da.Fill(dt);
            return dt;
        }
        catch (Exception e)
        {
            throw new Exception("Database error :\r\n" + stringB + "\r\n" + e.Message, e);
        }
    }

Now this i my function, The error gets thrown at

da.SelectCommand.Parameters.Add("@" + conditionColumns[i], (DbType)conditionValues[i]);

with the error

Database error : SELECT * FROM ANIMALS WHERE (animal_number = @animal_number) InvalidCastException

I am not sure wat to do now, i cast DbType since its the only type it seems to accept, but still throws the error.

Soner Gönül · Accepted Answer · 2015-11-21 21:34:29Z

1

Since conditionValues[i] returns object, you can't explicitly parse it to DbType.

You can check your object with is operator to get it's compatible type or not.

For example;

if(conditionValues[i] is int)
{
     da.SelectCommand.Parameters.Add("@" + conditionColumns[i], DbType.Int32).Value = conditionColumns[i];
}

answered Nov 21, 2015 at 21:34

Soner Gönül

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3 Comments

Black Lotus Over a year ago

Seems to have fixed it, Thanks

Black Lotus Over a year ago

So quick question that als has to do with casts, i am trying to pull a item from my SQLite database like this animal.FeedScheduleType = (BcFeedScheduleType)drAnimal["feedschedule_type"]; Where BcFeedScheduleType is a public enum, Now it throws me a InvalidCastException you have any idea why? or how to fix that?

Black Lotus Over a year ago

Try something like animal.FeedScheduleType = (BcFeedScheduleType)Convert.ToInt32(drAnimal["feedschedule_type"]);

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