Member Avatar for Fenerbahce

command.Parameters.AddWithValue("@number", TextBox1.Text)

can i do this from another way?


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  • Latest Post Latest Post by yoteksin

Dani AI

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The error occurs because the DataAdapter is executing a command that does not have the parameter defined. In 's snippet a SqlCommand object is created and a parameter is added to it, but the adapter is then constructed from the SQL text and connection — that causes the adapter to create its own SelectCommand without the previously added parameter. That is why SQL Server complains that the variable (for example, '@number') was not declared. is on the right track: either add the parameter to the adapter's SelectCommand, or (cleaner) give the adapter the actual SqlCommand that already contains the parameter.

A robust fix pattern: build and validate the input, add a typed parameter to the SqlCommand (avoid blind use of AddWithValue), and construct the SqlDataAdapter from that SqlCommand. Use Using blocks so connections/commands are disposed. Example (replace placeholders with your table/column/connection):

Using cn As New SqlClient.SqlConnection(connString)
    cn.Open()
    Using cmd As New SqlClient.SqlCommand("SELECT * FROM YourTable WHERE YourKey = @id", cn)
        Dim parsed As Integer
        If Integer.TryParse(TextBox1.Text, parsed) Then
            cmd.Parameters.Add("@id", SqlDbType.Int).Value = parsed
        Else
            ' handle invalid input
        End If

        Using da As New SqlClient.SqlDataAdapter(cmd)
            Dim dsResults As New DataSet()
            da.Fill(dsResults, "results")
            DataGridView2.DataSource = dsResults
            DataGridView2.DataMember = "results"
        End Using
    End Using
End Using

Troubleshooting notes: inspect the adapter's SelectCommand and its Parameters collection before calling Fill to confirm parameters are present; prefer explicit parameter types (SqlDbType) over AddWithValue; validate/parse TextBox input to avoid runtime conversion or SQL type mismatches; and always close/dispose connections. In short: make the adapter use the same SqlCommand that holds your parameters (or add them directly to adapter.SelectCommand) and the "Must declare the variable" error will disappear.

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Member Avatar for Paladine

Not sure what you are asking? Why can't you use this method?

Member Avatar for Fenerbahce

when i try to search something, program give me this error; Must declare the variable [EMAIL="'@number'"]'@number'[/EMAIL] on this line; DataGridView2.DataMember = "mutsuz".


full code is this.


Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click


Dim baglanti As New SqlClient.SqlConnection()
Dim dataadapter As SqlClient.SqlDataAdapter
Dim command As New SqlClient.SqlCommand
Dim dataset As New DataSet
baglanti.ConnectionString = "data source=zengin\instance2000;" & "initial catalog=inandbf;" & "integrated security= SSPI"
baglanti.Open()
command = baglanti.CreateCommand
command.CommandText = "select number, name, surname from veriler where number=@number"
command.Parameters.AddWithValue("@number", TextBox1.Text)
dataadapter = New SqlClient.SqlDataAdapter(command.CommandText, baglanti)
dataadapter.Fill(dataset, "mutsuz")
DataGridView2.DataSource = dataset
DataGridView2.DataMember = "mutsuz"
baglanti.Close()
End Sub

Member Avatar for Fenerbahce

sorry, error comes on this line dataadapter.Fill(dataset, "mutsuz")

Member Avatar for yoteksin

Try the following intead of
command.Parameters.AddWithValue("@number", TextBox1.Text)

dataadapter.SelectCommand.Parameters.AddWithValue("@number", TextBox1.Text).

Sampiyon FeNeRbAhCe

Edited by yoteksin because: duplicate
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