How can I make the program select different selected items from a checklistbox and update one mysql column?

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Hi, I found something here that say to use for for this thing..
I try to used like that:

VB

For Each ItemSelecionado In CheckMaterial.CheckedItems
    conn.Open()
    cmd.CommandText = "Update material SET `Quantidade` = `Quantidade` - 1 WHERE `Nome` = '" & CheckMaterial.CheckedItems.Item(ItemSelecionado) & "'"
    cmd.CommandType = CommandType.Text
    cmd.ExecuteNonQuery()
    conn.Close()
Next

But the program give me this error:

"The conversion of the string  "Ram 1gb [DDR]" To type ' Integer ' is not valid."

How Can I resolve that?

What I have tried:

VB

For Each ItemSelecionado In CheckMaterial.CheckedItems
    conn.Open()
    cmd.CommandText = "Update material SET `Quantidade` = `Quantidade` - 1 WHERE `Nome` = '" & CheckMaterial.CheckedItems.Item(ItemSelecionado) & "'"
    cmd.CommandType = CommandType.Text
    cmd.ExecuteNonQuery()
    conn.Close()
Next

Posted 21-Apr-18 12:30pm

Member 13780554

Updated 21-Apr-18 18:49pm

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Wendelius · Answer 1 · 2018-04-21T18:50:00

Solution 1

Based on the error message, it seems that the column Nome in the database is defined as integer. So you should either change the column data type or use some other (integer) property from the CheckMaterial in the condition.

Another thing is that to avoid conversion problems and SQL injections during the SQL statement execution, you should use OleDbParameter Class (System.Data.OleDb)[^] . For more information, have a look at SQL injection - Wikipedia[^]

Posted 21-Apr-18 18:50pm

Wendelius

Comments

Richard Deeming 24-Apr-18 10:38am

Isn't it more likely that the Quantidade column isn't defined as a number, and the error comes from trying to subtract 1 from a string?

Wendelius 24-Apr-18 12:36pm

Could be, but the error message

The conversion of the string "Ram 1gb [DDR]" To type...

feels more like it's related to the name, not quantity