How to Fix the 'Parameterized Query Expects Parameter Which Was Not Supplied' Error?

Troubleshooting "Parameterized Query Expects Parameter Which Was Not Supplied" Error

When executing a parameterized query in your code, you encountered an error indicating that a parameter was not supplied. To resolve this issue, let's examine the code and apply a fix.

In the provided code snippet, a parameterized query is being used to retrieve records from a database based on a search parameter from TextBox2. However, the error message suggests that the '@Parameter1' parameter is not being supplied. To fix this, we need to explicitly add and assign values to the parameters in the 'Parameters' collection of the command object.

The following code modification will address this:

Dim cmd As New SqlCommand
cmd.CommandText = "SELECT * FROM borrow WHERE Department LIKE '%' + @Department + '%'"
cmd.Connection = con
cmd.CommandType = CommandType.Text
cmd.Parameters.Add("@Department", SqlDbType.VarChar)

If Not TextBox2.Text Is Nothing Then
    cmd.Parameters("@Department").Value = TextBox2.Text
Else
    cmd.Parameters("@Department").Value = DBNull.Value
End If

con.Open()

In this modified code, we:

• Add a parameter with the name "@Department" to the command.
• Check whether the text in TextBox2 is not null (to handle empty search input).
• If the text is not null, assign the value from TextBox2 to the parameter; otherwise, assign DBNull.Value to handle null input.

The DBNull.Value is used to represent null values in database operations. By adding this check, we ensure that the query will execute correctly even if the search input is empty or null.

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