Why Does My SQL Stored Procedure Throw a 'Procedure or function '...' expects parameter '@parameter name', which was not supplied' Error?

Stored Procedure or Function Expects Parameter That's Purportedly Supplied

When calling a stored procedure to insert data into a SQL Server database, you may encounter the error "Procedure or function ' stored procedure name ' expects parameter '@parameter name', which was not supplied." This error message can be perplexing, especially if you have verified that the stored procedure has the correct parameters and that they are being supplied in your code.

Troubleshooting the Error

To resolve this issue, thoroughly review the following:

• Verify Parameter Names and Data Types: Ensure that the parameter names and data types in your code exactly match those defined in the stored procedure. Use the same casing and avoid any typos.
• Check Command Type: Specify the command type as StoredProcedure to explicitly indicate that you are calling a stored procedure. Omitting this setting can lead to ambiguity about the command being executed.
• Disable Default Values: If default values are defined for parameters in the stored procedure, they must be explicitly specified in your code, even if you do not want to provide custom values.
• Parameter Ordering: The order of the parameters in your code must match the order defined in the stored procedure. If a parameter is missing or out of order, the error will occur.

Sample Code Update

Here's an updated version of your code that explicitly specifies the command type and parameter values:

public void SHOWuser(string userName, string password, string emailAddress, List<int> preferences)
{
    using var dbcon = new SqlConnection(conn);
    using var cmd = new SqlCommand();

    cmd.Connection = dbcon;
    cmd.CommandType = System.Data.CommandType.StoredProcedure;
    cmd.CommandText = "SHOWuser";

    cmd.Parameters.AddWithValue("@userName", userName);
    cmd.Parameters.AddWithValue("@password", password);
    cmd.Parameters.AddWithValue("@emailAddress", emailAddress);

    dbcon.Open();
    int i = Convert.ToInt32(cmd.ExecuteScalar());

    cmd.Parameters.Clear();
    cmd.CommandText = "tbl_pref";

    foreach (int preference in preferences)
    {
        cmd.Parameters.Clear();
        cmd.Parameters.AddWithValue("@userID", Convert.ToInt32(i));
        cmd.Parameters.AddWithValue("@preferenceID", Convert.ToInt32(preference));

        cmd.ExecuteNonQuery();
    }
}

By carefully inspecting the parameter names, data types, command type, and parameter ordering, you can alleviate this error and successfully execute your stored procedure.

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