使用 javascript 验证 WebForm

问：

我的提交按钮上有两个事件。一个是 OnClientClick，第二个是 OnClick。OnClientClick 用于验证表单，OnClick 用于在数据库中提交记录。首先，我想验证表格，然后应该提交。如何实现这一点。

<script type="text/javascript">
    function validateSection4() {
        var txtIDProof = document.getElementById('<%= txtIDProof.ClientID %>');
        var txtIDNumber = document.getElementById('<%= txtIDNumber.ClientID %>');
        var fileIDPhoto = document.getElementById('<%= fileIDPhoto.ClientID %>');
        
        var file = fileIDPhoto.files[0]; // Get the selected file

        var isValid = true;
        var lblIDProof = document.getElementById('<%= lblIDProof.ClientID %>');
        var lblIDNumber = document.getElementById('<%= lblIDNumber.ClientID %>');
        var lblIDPhoto = document.getElementById('<%= lblIDPhoto.ClientID %>');
        var allowedExtensions = ["jpeg", "jpg", "png"];
        var maxFileSize = 100 * 1024; // 100 KB in bytes

        // Clear previous error messages
        document.getElementById("lblIDProof").innerText = "";
        document.getElementById("lblIDNumber").innerText = "";
        document.getElementById("lblIDPhoto").innerText = "";

        // Validate ID Proof dropdown
        
        if (txtIDProof.value.trim() === '') {
            lblIDProof.innerHTML = 'Please select an ID Proof.';
            isValid = false;
        }

        // Validate ID Number textbox
        if (txtIDNumber.value.trim() === '') {
            lblIDNumber.innerHTML = 'Please enter the ID Number.';
            isValid = false;
        }

        // Validate ID Photo upload
        if (fileIDPhoto.files.length === 0) {
            lblIDPhoto.innerHTML = 'Please upload the ID Photo.';
            isValid = false;
        }
        else {
            var fileExtension = file.name.split('.').pop().toLowerCase();
            var fileSize = file.size;

            // Check file extension
            if (!allowedExtensions.includes(fileExtension)) {
                lblIDPhoto.innerHTML = 'Only jpeg, jpg, and png files are allowed.';
                isValid = false;
            }

            // Check file size
            if (fileSize > maxFileSize) {
                lblIDPhoto.innerHTML = 'Maximum file size allowed is 100KB.';
                isValid = false;
            }
        }

        return isValid;
    }
</script>`